How crowded in April?

There were crowds of tourists in France when we visited April 2014. It's a very popular country and for good reason. I couldn't imagine crowds in high season.

Springtime in Paris is wonderful! The crowds will be there but you can manage things with a little planning. If museums are your thing, make sure to get the Museum Pass and not wait in lines. I have never been to the Grotte, but if you want to see it, GO! I would do a little research ahead of time to maximize your visit there.

Font de Gaume restricts the number of visitors to 80 per day and the number in the cave at one time to 13 or so. This information on how to get tickets is from the official website. I edited it to include Font de Gaume only and to coincide with your time in France.

In English:

Grottes de Font-de-Gaume
Open daily except Saturdays
16 September - 14 May 9:30 am - 12:30 pm and 2 pm - 5:30 pm
Font de Gaume Cave : for conservation reasons, access limited to 80 person/day
No reservation available, all the tickets are sold at the entrance every day for the day.

The website is in English as well as French, but not everything is translated. You may have to run it through Google Translate.

The information in French tells another story:

Grottes de Font de Gaume: pour des raisons de conservation, nombre de places limité par jour
Billets en vente sur place le jour même, dans la limite des places disponibles.
En 2014, il est possible de réserver ses billets pour Font de Gaume pour 2 visites :

• en basse saison : 15h15 (13 places) et 16h (13 places)

Ces réservations doivent être faites par courriel : fontdegaume@monuments-nationaux.fr
ou par téléphone de 14h à 16h30 : 05.53.06.86.00

And from a commercial B&B website:

In 2013 the world famous for it’s original cave paintings Font de Gaume decided they would no longer take online reservations for visits. This meant that you could only get one of the limited 80 tickets per day by queuing VERY early in the hope of getting lucky. This also meant that thousands of travelers from around the world, that came to see the paintings were turned away.

Font de Gaume learned from this debacle and as of 2014:
Font de Gaume will still allocate a total of 80 tickets a day
2 allocated a tours a day totaling 26 [ 13 per tour ] tickets will be RESERVATION only
The remaining 54 tickets will be based on 1st come 1st served, sold at Font de Gaume
This new arrangement means that visitors can now turn up at Font de Gaume and purchase a ticket for any day of the week, giving visitors a MUCH better chance of getting to see the cave art.

If Rick says not to bother, I disagree. It was amazing. It is just very difficult to get tickets.

Lascaux II is a replica, but also amazing. We saw both in October, 2009. It was not crowded then, so it might not be so crowded in April.

Be aware that if you do make it into Font de Gaume, you will not be allowed to carry anything into the cave. There is a place next door to the entrance where you can lock up your stuff. The path inside is paved but often very narrow, low and somewhat difficult to walk through. You also have to walk a narrow, steep uphill path on the side of the hill to get to the entrance. Lascaux II is much easier to get to, more open and has fewer rules for visiting.

There is much more than these two caves to see and do in the area. I hope to make it back someday with more time to spend. I can recommend Les Cordeliers as a place to stay in Sarlat. And if you won't have a car, I can recommend Phillippe to take you around the area. He is a wealth of information and showed us some places we would never have seen without him. My favorite was the Maison Forte de Reignac, built right into a cave.

I was in Paris last 2 weeks of April this year. There were lots of tourists (there always are) but not as nearly as many as in June or September. It was explained to me that pretty much all of France is on holiday for 2 weeks around Easter (school holidays). The country is divided into districts, roughly half the population is off the first 2 weeks, the rest the last 2 weeks. So you have more French tourists then . . . not so much in Paris, but in other places. Easter's early in 2016, so you should miss most of it - and I'm not even sure how much of an impact it makes.