I just wanted to add that Semana Santa (Holy Week) is a very busy time (big vacation time for Ticos) on the beaches and one of the most expensive times too. You may see prices increase during that time. If you have trouble finding something that week or notice prices are super high, it may be a good time to visit some places inland and then return back to the beach after Easter. Just an idea. 🙂
Have you thought about which beach area you prefer? Choose from the following: Guancaste, Nicoya, the Central Pacific coast, the South Pacific coast, or the Carribbean coast.
Guanacaste is the dryest area and the South Pacific and Carribbean are the wetest ones. Yet March and April are the end of the dry seaon in Costa Rica.