Not to long ago I got back from a min-vacation to the Caribbean coast and beaches are on my mind. If you make it all the way to Costa Rica, I would advise you to write an extra day or two into your itinerary to spend on the beach. You are truly missing out if you don’t. The beaches are gorgeous and relaxing, they attract interesting people, and they offer up plenty of activities to keep you busy (surfing, snorkeling/diving, wildlife spotting, etc.) even if you aren’t into just lounging around on the sand and taking in the sun.
I would then advise you to listen to where everybody tells you to go and then not go there. There is nothing wrong with where they are telling you to go but with endless sand in either direction, you can do better, and you can get away from any crowds in the mean time.
When I was in Puerto Viejo de Talamanca earlier this week I took a day to just walk along the beach. I intended to catch a bus to Punta Uva, a well-known beach in the area, and walk back to my hostel from there. I ended up missing the bus stop and didn’t get off until Manzanillo, a town 5 km later. I had just planned to walk the beach that day anyways so it didn’t matter to me if I started from Puta Uva or Manzanillo. I ended up wandering for just over 8 miles. I saw a lot of sand. I also saw something that I found quite interesting; people did not seem to congregate at the most beautiful spots but rather seemed to gather wherever there was easy road access. This was great news for me since I was able to have the most gorgeous areas all to myself. All it took was walking maybe 15 minutes from a popular spot and I was in deserted area. The extra steps that it took to get away from the crowds were completely worth it in my opinion.
The flip side of the coin is that being alone isn’t always ideal. Almost all of the shops and businesses catering to tourists are going to be in the populated areas. If you want to rent a surfboard or beach cruiser or go on a dive then finding the popular areas is exactly what you want to do. I didn’t want to do any of that that day so I simply got away from the people (which was surprisingly easy to do).
Whatever you prefer, there is a Costa Rican beach with your name on it. From what I have seen, there are beautiful beaches on both the Caribbean and the Pacific coasts. The pacific side is slightly more built up and “touristy” while the Caribbean side is a bit more laid back and has a palpable “Caribbean” vibe to it. In all honestly, it wouldn’t be a mistake to choose to go to either coast, the only mistake would be choosing to not go at all.