20 day trip to Spain, Greece and Croatia?

Is that budget 4500 for BOTH of you? So 2250 each? It would help to know that. If you're budgeting 2250 each, including flights, in June of this year, you're going to have to cut way back on your itinerary.

Even if you have 4500 each to work with, this is a tough itinerary because you've chosen places that are quite far from each other. With 20 days, you've got 18 nights in Europe and in that 18 nights you want to cover at least 2 places in Spain, 2 in Greece and 3 in Croatia.

It's possible you could figure this all out on a very very rushed trip, but I think you'd be happier if you pared this down a bit. Transiting, whether by airplane or train, really starts to add up after awhile and it will affect your budget as well as eat up A LOT of time.

These are all beautiful places, but can you pick maybe 2 countries instead of 3 to make it more manageable and less expensive? You'll surely be back in Europe again since you loved it and you can cover more ground next time.

Book the trans-Atlantic flights as an "open-jaw" or "multi-city" trip. Look for that term, which will split any difference between roundtrip rates to/from your first and last cities. One-way tickets are almost always much more expensive for this part of the trip.

Within Europe, budget airlines do base their rates on one-way flights, with no roundtrip discount. Try www.skyscanner.com, instead of just Vueling. Some flights won't run every day, so test a few scenarios. You can also put in the request in general terms, from country to country, rather than city to city, to find more options. Greece to Croatia is typically a much more difficult connection than people assume; flying is the way to go there, too, even with a connection.

It's not just that your 3 countries are far apart (requiring flights); you've got hard-to-reach destinations within two of them. Even Dubrovnik to Plitvice Lakes might be an entire day on the bus. And if you plan ferries to and from the islands and they get canceled because of weather, a compressed trip will fall apart completely.

I estimate that you would have to spend a major portion of 8 or 9 days in transit on this proposed 20-day trip, leaving not nearly enough time to see things at your destinations. If you choose two of your countries it will work better, but you still may spend a lot of time in airports. You could have a much nicer and much less expensive trip if you stuck to a more limited geographical area.

Each of your countries has many wonderful destinations and is worth more than 20 days by itself. Crete, for example, is a relatively large island. It's my top choice of the three islands you mentioned, but Mykonos and Santorini are very popular with young folks who enjoy nightlife. You could spend more than a week on Crete alone (staying in at least two different cities) and fill in the rest of the time on other islands and the Greek mainland.

Croatia's capital, Zagreb, is very lively and was full of college-age residents and visitors when I was there last August and October. It's not on the coast but is a very popular destination. There's lots of beautiful coastline, and many beautiful islands, between Dubrovnik and Zagreb. Plus Plitvice Lakes. All accessible by low-cost, though not speedy, public transportation (more buses than trains). Or you could branch out a bit to visit Montenegro (near Dubrovnik) or Ljubljana, Slovenia, another lively, youth-oriented city, that's not too far from Zagreb.

I'm not sure about the current cost level in Spain, but if you limit your trip to Greece or Croatia and sleep and eat on the cheap, you may have some money left over to put toward your next trip, during which you could visit one of the two remaining countries.

I'd look at the transatlantic flight costs and base my decision on that. I'd expect Spain to be quite a bit cheaper. If it isn't, this might be the year to go to Croatia or Greece.

Sorry, but you're way behind in planning if you are considering a holiday in 3 months time, particularly one so complex. You are traveling in peak season and internal flights around Europe have been available for months and their prices only head in one direction. So you are too late to get the best flight deals, so you need to nail your itinerary asap and get booking!

The countries that you have picked are not the best connected and from a budget perspective, Santorini and Mykonos will swallow too much of your budget. Crete is the more interesting of your Greek options, but I doubt that you will be able to get direct flights from Croatia. Pick Two countries not three to maximise your time and fit your budget.

Book open jaw to maximise your time.

On Trip Advisor, most people recommend 1.5/2 weeks to cover Krka and Plitvice to Dubrovnik. You could combine this with Barca then a few days on a beach in Spain before heading home.

Like others have said, places you want to visit are spread out, which means a few days will be spent in travel, but it's possible.
I'd fly into Athens, then fast ferry or flight to Mykonos (3 nights), ferry to Santorini (2 nights), fast ferry/flight to Athens then flight to Dubrovnik (look month view on skyscanner to see what days they fly this route, looking at $164+ for June), 1 night in Dubrovnik (visit Montenegro) one way sail with Sail Croatia 7 nights Dubrovnik to Split (Explorer cruise-different type of cruises depending on your age) Stay for 1 night in Split (visit Kraka or Mostar), fly Split to Barcelona 2 nights (budget flight route $68+, but check days on skyscanner month view), ferry/fly to Ibiza-3 nights, (do cruise with Busabout or similar company), ferry/flight back to Barcelona then train to Madrid and fly out of Madrid.
I'm coming from Australia and I know I can fly into Athens, and out of Madrid for a reasonable price, but don't know if that would be the same from Canada?
It;s very rushed. I'd cut out one country to maximise your time, see more, and not waste so many full days traveling when you have less than three weeks.
Have fun!!!!

The logistics for what you want to do will make this trip seem like you are constantly in transit. Unfortunately that's the joy that comes with choosing island destinations (Mallorca, Santorini, Mykonos) and places not blessed with many flight options (Croatia). One third of your valuable holiday time will be lost to getting between your destinations. A 20 day trip from Canada means 18 nights spent in Europe. Look at your dates and see if you can make it work with flights and ferries by visiting ... www.rome2rio.com ...and... www.skyscanner.com

Your best case is something like this...
Barcelona - 3 nts
Palma de Mallorca - 3 nts
Dubrovnik - 3 nts
Split - 2 nts (perhaps island hopping between)
Santorini - 3 nts
Mykonos - 3 nts
Athens - 1 nt

Unfortunately you will find the best flights do not operate daily, and you may have to take an awkward routing with a long connecting time. Have a go and see what you can make work. I think you will become stuck quite quickly and need to reconsider.

DJP beat me to it, but I just want to emphasize that before you get too attached to the places you want to visit, use Rome 2 Rio to investigate transit links. It's not foolproof, but it's a good start for learning how to connect places. You'll quickly see what everyone on this thread is talking about - your destinations simply don't combine well. It's like trying to connect Nantucket and Telluride - there's just no fast or easy way to do that.

To find flights within Europe, Skyscanner will search for multiple airlines, not just Vueling.

Thanks everyone for your advice! We took the advice and decided to shorten it to two countries (Greece, which I really want to visit and he picked Spain). Croatia will have to wait until next year maybe!!! We will now get to spend more time in each of these two countries and less time travelling. We decided to book ferries in Greece, and fly Ryan Air from Athens to Barcelona. We also booked our flights into Europe through FlightNetwork and got a great deal! Thanks everyone:)

That makes good sense, and is the choice I would have made. Happy planning.