month long trip Portugal Spain France Italy

I think you'll find that Spain and France are pretty large countries. And from Barcelona over to northern Italy is a long way.
Look into flying one of the budget European airlines if the train trip is over 3 hours.

We flew from Granada to Barcelona, and it was an hour by Vueling's jet plane alone. From Barcelona in SE Spain to Paris, it's 650 miles and 6.5 hours on a fast train.

If you choose to visit Tuscany hilltowns, a rental car is just about mandatory. Roads are well paved, easily navigated however just a little crooked.

Portugal is not one of those postage-stamp places. I wouldn't want to leave there after seeing not much more than Lisbon and Porto, but I suppose you could do that.

You'd definitely want to fly from Portugal to Barcelona. Ground-transportation links between those two countries are limited and slow.

I'm comfortable with a week for Barcelona--though I stayed longer since I'm a nut for modernista architecture. You might even have time for a side trip or two. There's a lot more to see in Spain, but there's no rule that says you have to try to cover the entire country in one trip (which you wouldn't be able to do in a month, anyway).

What does "southern France" mean to you? It's a large area. A week would be tight if you wanted to see some places in both Provence and the Riviera, even if you were willing to skip other regions of the south. I'd rather have more than a week unless I was focusing only on Provence or only on the Riviera, but I am a slow traveler who likes to go to some less-touristy spots, and I like to spend a lot of time walking around every city and town I visit.

Depending on your first stop in France, it might be practical to take the train from Barcelona. However, if your target is the Riviera rather than Provence, it would be more efficient to fly from Barcelona to Nice; traveling by rail would take 8 hours or longer, I think.

If your French time ends on the Riviera not too far from Nice, you'd be looking at about 7 hours or a bit longer for the trip to Florence by train. Many people would fly that link. The airport in Pisa is larger than the one in Florence, so you might have more flight options there. Or you could just as easily fly into Venice and hit Florence later. Flying home from Venice, for many people, means an extremely early departure for the first flight, which can require super-expensive water taxi service to get to the airport on time.

Rail service between Florence and Venice is frequent and rapid--as fast as 2 hr. 15 min.

A week for Florence and Venice will keep you rather busy, but that's more time than a lot of travelers allow. It won't really be long enough to see much of rural Tuscany, which is high on many visitors' lists.

I'd prefer a trip that doesn't cover so much geography and require so many mid-trip flights or very long train rides, though this is very much a matter of personal interests and travel style. I'd recommend being sure of your priorities before buying airline tickets. You don't want to commit to flying into Portugal and out of Italy before you've done some guidebook research, at least on southern France. It's easy to imagine that you might end up with such a long list of French stops that you decide the trip needs to end there.

I have to disagree with most of what was said by David above, apart from the fact that Spain and France are large countries.

It may have been a 1-hour flight from Granada to Barcelona, but what about the time it took to get to the airport, the 2 hours one it supposed to allow to get through security, and the time to travel from the Barcelona airport to the city itself and their hotel?

It sound like you are thinking of moving fromPortugal across northern Spain into southern France and then to Italy. That is a fairly straightforward path and can all be done by train. You have enough time in each country to break up the travel into 3-4 hour segments and explore along the way.

And yes, there are some hill towns in Tuscany are best reached by car, but I do not see any of those on you wishlist. You can’t even have a car in Venice, and no one wants one in Florence because of the ZTL’s.

We want to wander and explore. But perhaps we are trying to do too much in the time we have.

I have visited all these countries several times. Your itinerary was way too packed with too much travel.

Travel between places takes away for the time you can spend enjoying your trip, savoring them. Don't do fast food, do a nice sit down meal with wine taking hours.
Portugal may seem like a small country, but my list trip there was over two weeks.

I suggest doing only Portugal and Spain, or S. France and Italy.

If you don't want to do that, then fly into Barcelona, then proceed to S. France, then do Italy.

If you really want to wander and explore, one week per country or region will be too short, or you will have to revise your explorer standards.

Portugal with Lisbon, Porto, the coast, Coimbra, the Douro River region, and possibly the center. It's well over 10 days.

Barcelona itself is not representative of Spain but of Catalonia, so if you go to Barcelona only you will not have really seen Spain. Spain, Madrid, Castilla, Valencia, etc in addition to Barcelona would involve at least 2 weeks.

The South of France is rather big too. From the Spanish border, to the Italian border it is more than 500 kms crossing very different styles of regions. Even by only going along the Mediterranean coast, 10 days would not be too much.

As for Italy, I don't imagine that you can explore it in less than 15 days. Listing the places to see in Italy from Florence to Sicily would take up too much time in this post.

Add to all this the transfer times from one place to another and it will take you two months.

That said, the notion of "explore and wander" being very subjective, I know that when people say they want to do that, it's sometimes quick exploration consisting of hanging out for a few hours in a place then leaving the next day in another.

So in this case, one week per country will be more than enough.