Prepare to get wet. Even during the dry season, December through April, high humidity's and rainstorms make everything damp. The temperatures fluctuate minimally, with an average in the high 70s Fahrenheit. Mountain regions will be slightly cooler than lowlands, but Costa Rica is set in the tropics, so that is a relative idea.
Lots of beans and rice, with a heavy influence of seafood near the coastlines. One of the most delectable breakfast dishes in the world comes from Costa Rica: Gallo Pinto. It is a mix of beans, rice, beef, eggs, and plantains, popularly covered with salsa. Caribbean cuisine is the main influence along the southeast coast of the Limon province
Costa Rica uses the same electrical system as the USA. Anyone traveling from North America should not need an adapter.
The "colone" is the typical currency. Businesses do accept the US dollar, and give change in a fair exchange rate in colones. Customs does not do a good exchange rate, so have all of your colones spent by the time you leave.
Some of the outlying villages do not have modern technologies, but urban areas and resorts in Costa Rica accept plastic. There are ATMs available.
Costa Rica is technologically equipped. The Internet is available. Cell phone service depends on the carrier. International prices are extremely high, in general. Check with your service provider before traveling.