Spain, Portugal, and Monaco

Hi,
May I ask why Monaco? There is about 6 hours' worth of sightseeing there, if that... and it feels a bit soulless in my opinion (granted, my last visit was on a weekend in mid-December).

Also do you have any interest in any of the places between Spain and Monaco, such as Arles, Aix en Provence, Nice...? Or in neighboring Italian regions? If so, it might make more sense to visit in a future trip to those areas...

But if Monaco is a must-visit for you, then Nice is the local airport and has direct flights from Lisbon, Madrid and Barcelona, plus maybe other cities.
The drive from Barcelona is very long and traffic prone: if you do not wish to visit the in-between places, then do not drive.

When? The pandemic is not over yet and crossing borders can still be an issue.

But, flying open jaw sounds like a good idea if you want to visit Monaco, to Lisbon and from Nice would be my choice. Not driving to Monaco will save you a lot of money in car drop off fees. In normal times there are high speed trains from Barcelona to Marseille where you can change to another train to Monaco.

@balso @Badger
I've always wanted to visit Monaco. I know it is a day trip, so will plan on spending the rest of the time in Cannes, San Remo, and Nice. I don't know of anything that's on the way from Barcelona, but when driving, we love to explore and stop at unplanned places. However, after more research I think we'll opt out to fly into Nice, settle, rent a car there and drive down to that area. Thanks!

Iina, we ended our RS Loire to the South of France Tour in Nice. We loved Nice! This was September 2013. Some of our tour group stayed an extra night to do a day tour to Monaco. The scenery was gorgeous. We took the bus there and the train back to Nice. We all enjoyed visiting the Cathedral, changing of the guard at the palace, a glance at Monte Carlo and a wonderful lunch at a seaside restaurant to celebrate the end of a grand tour. Enjoy your planning!

…will plan on spending the rest of the time in Cannes, Sorrento, and Nice

Sorrento, IT?

@MaryPat oops. Meant to say San Remo!

OK, clearer for me now!
So, yes, you could definitely arrive in Nice, spend 4-5 days exploring the places you mention, then fly to Barcelona.
As suggested above, look into multi-city flights into Nice (connection required unless your home airport is JFK at some times of the year) and out of Lisbon.

what month of the year will this be?

Traffic varies from time to time in the area, but in the season traffic along the Rivieras is a real bear. Take it from somebody who's driven there several times (from home here in England).

Not only is traffic a real pain most of the time in Nice, parking is abysmal. The tram is your friend.

Easy, frequent, fast, inexpensive trains link all the Riviera towns, on both sides of the Italian/French/Monegasque border.

I actually find driving in Monaco, except in and around Grand Prix Weekend, easy and straightforward, as long as you don't want to go up the Rocher (police in white uniforms only allow certain cars up the Rocher) and parking is very easy. Monaco has many (about 40) multistorey car parks (the one next to the station is something like 14 levels) and an hour free parking is available at all public ones. For access to Rocher it is best to park at the fisherman and take the elevator up to the top of the rock, just around the corner from the aquarium and close to the palace.

You probably know, but San Remo no longer provides the flowers for the Vienna New Years Day concert.

I don't know how much time you have allowed for your trip, but having been to Spain and Portugal several times, as well as Monaco, you need to focus on less ground. Monaco is out of the way.

On our last trip to Portugal, we spent two weeks there and didn't go to the Algarve.

To do Spain right, you need to visit, Barcelona, Madrid (day trips to Segovia and Toledo), Cordoba, Seville, Granada, Malaga and possibly Valencia. If more time take in the Basque region in the north and Galacia in NW. It would take a month to do all that.

Thanks, everyone. Lots of planning is in order!

You haven't told us when you plan to travel. I was in Nice in mid-March about 3-4 years ago. It was very easy, cheap and efficient to get around by local train to the coastal towns. It looked like there wouldn't have been a problem finding nearby parking in any of the towns - except possibly Nice - but I don't think it would be more convenient - unless you want to go inland where bus/train service may not be as good. If you're going later in the year, expect there to be much more traffic and many fewer parking opportunities.

Thank you @balso and everyone else!
@Chani we are thinking March, as well. I don't like when it's too hot and when it's nice for me might be cold to others.

Of all the excellent day trips one can take from Nice, Monaco was our least favorite. Antibes and Cap Ferrat were our hands down favorites.

Monaco (and Nice) can be quite pleasant in March. I'm often there in February and it's pretty decent then....