2 week trip-Spain, France, Italy

That is a lot of traveling in a short time period. It's too bad you have to return to Barcelona to fly home. Two nights in a place is equal to only one full day. At the end of December in Paris it doesn't get light until around 9:00 a.m. and it's dark by around 4:30 p.m. For only one full day there it wouldn't be worth the trouble to get there. I can't believe I'm saying that. Paris is my favorite city. How do you plan to travel? Train? Low cost airline? Where in Italy do you want to go? I'm counting 12 nights in Europe. Is that correct? You might consider doing something like this - Arrive Barcelona. Fly to Nice (5 nights) Fly/train from Nice to Paris or fly/train to somewhere in Italy (4 nights) Fly to Barcelona (3 nights)
Fly home Save your time in Barcelona for the end of the trip to minimize checking in/out of two hotels there.

Leaving Barcelona for the end of the trip is a great idea! I figured we'd go to Florence since it seems fairly close to Nice, but maybe skipping that would work better. We were thinking to travel by train; I'm trying to figure out how all that works. Not going to lie, I'm a little stressed thinking, how are we getting from the airport to the train station, from the train station to WHEREVER we're staying, WHERE are we staying, what site's do we see, what do we avoid...ugh! I've never been out of the country so this is all new to me.
Really appreciate your help!

It is a 10+ hour train trip from Barcelona to Nice. I would fly. Can you possibly change your airline ticket to fly to Nice instead of Barcelona? If not, allow plenty of time between arriving in Barcelona and flying to Nice. In addition to clearing customs and immigration in Barcelona, you need to allow time in case your original flight is delayed. Paris is beautiful that time of year and has many indoor activities to do in case the weather is bad. It is a 5+ hour train ride from Nice and you arrive in town, so you can easily take the metro from the train station to wherever you are staying. I recommend a place in the 4th, 5th or 6th arrondissements to be central to most places you would likely go. Taking the train from Nice to Florence takes 7+ - 9+ hours, depending on which train you take. I would then fly to Barcelona to finish the trip out. There is a train from Paris to Barcelona that takes just over 7 hours, so that is also an option.

Andrea and my wife and I are both aware of how "wiped" you can be after landing in Barcelona after a long trip from the West Coast. Andrea and I are members of the Sacramento RS travel group and she was 4 days behind us last year on a trip to Barcelona and France. Usually, we can arrive, go to our hotel, drop our luggage and go out touring. We were quite tired on the afternoon of our arrival. My comment is that 2 weeks is a very short time to visit 3 countries. Our trip last year was for 3 weeks and we spent 4 days in Barcelona and the remainder in a part of France. With this much time, we could only see Eastern France and Paris/Versaille. At best, you will only have a few days in a few places. Your travel time will consume more than you expect.

Thank you both so much for your tips! Will let you know how it goes...

What Larry says is true. Especially for those of use coming from the West Coast, it is a very long trip to get to Europe. You may or may not suffer from jetlag of varying degrees. I don't want to be discouraging. I just don't want you to set yourself up for failure. And in the winter with short daylight hours and possibly inclement weather it is harder to see as much. I hope your trip will be wonderful.

Mary, it is not clear to me what you want to see. I see little relationship between Barcelona, Nice, "someplace in Italy", and Paris. Unless you a a great art museum afficianado, I would not even consider Florence. Italy is way out of your way, especially as you are considering Paris. I would only go to Italy if you want to go to Rome. Agreed, while I have never done it in Europe, flying seems the only practical alternative. Given you time frame and distances, I would opt for only three destinations: Barcelona, Nice, and Paris. You will have approximately 4 days in each city. The one that might merit less is the one to which you have already assigned 5. Therefore, I would definitely skip Italy and limit to three destinations.

David has some good points. I would also drop Italy from this trip. Too many far flung places. Advice to fly between the cities is good otherwise too much time for train travel. I would also add that there are cheap discount airlines from Paris/Barcelona and often for a base price of $150 or so if you book early. And the flight is about 1 3/4 hrs. You can fly from Orly or Charles de Gaulle but do not choose Beauvais as it is far from the ciy itself and costs time and lots more money to get there. Other cities too have discount airlines.
Check Skyscanner.com which includes both regular airlines and the discount airlines. Remember I said BASE PRICE above. You MUST read the fine print carefully on the discount airlines as everything is charged separately, including seat reservations, early boarding, especially luggage, etc. Do NOT go over the weight or size requirements and be sure to choose the correct number of pieces of luggage you will put on board in your reservation. If not correct, your penalty may be more than the cost of the ticket. Italy is a destination on its own. And you could also go to many other places in Spain and France. You will spend much less time traveling and much less money if you stay in one country and absorb its many different elements.

Ok, we're skipping Italy & flying from Barcelona to Nice & from Nice to Paris (we'll take the train from Paris back to Barcelona just so we can say we took a train ride). Now I need to figure out lodging, quick! I was looking at hostels & B&B's but a friend of mine said his daughter stayed in hostels & came back with bed bugs...We want to stay in places that are central to "the action" but we don't want to spend a fortune because we're really just going to be sleeping there & out the rest of the time. Any ideas...suggestions???

What's the big draw of Nice (the city, not the adjective or the concept)? Unless you've been to Europe so many times you've already seen all the prime destinations in Spain and France (and judging from your posts, I'd guess this is not the case)...personally, I'd probably skip Nice altogether. With just 2 weeks (and you don't say if that's really two weeks there, or two weeks as expressed by wishful thinkers who actually only have about 10 days after they factor in travel time and jet lag recovery)...I'd just go Barcelona and one other major destination - Paris, or maybe Madrid or another part of Spain. With the trip coming up so quickly and zero planning having been done at this point, I'd be freaking out. The one thing you have in your favor is you're definitely going in the off season. You'll have limited daylight, but a better shot at decent accommodations. Still, I'd drop everything else in my life that I could and start booking rooms fast. I'm a believer in the axiom that the shorter your trip, the more detailed planning you need to do. First start by being honest with yourself on how much usable time you really have there: don't count the day you arrive or the day you depart (no matter what time that is); discount the first day there after your arrival (counts as half a day since you'll probably be jet lagged and possibly a bit disoriented). Any day you travel by air, you lose most of that day. Any day you travel by train or bus, you lose half the day. Count the days left and that's how long your trip really is. Hope that helps.

The OP states in her original post that she is going to Nice to visit family.

Ah, OK, fair enough.