In many foreign countries it is frowned upon to walk around exposing all kinds of skin like we do in the states. For example just because Costa Rica has a tropical and temperate climate does not mean you should walk around towns in your bikini, likewise even though they have been blessed by Mother Nature with abundant tropical jungles and fertile rainforests that does not pretend that men should dress like Tarzan, even if they have the body for it.
This is not to say that when you are in Costa Rica that you have to wrap yourself up. Even if clothing as a whole is determined by a society's cultural scene, its climate, and the manner its citizens live, Costa Rican clothing does not differ a great deal from any other Central or South American countries. All the same, in Costa Rica clothing has two main types. First you have the traditional Costa Rican clothing that is worn to symbolize the country's culture. This is also considered as their national costume and can be seen being donned by locals for folkloric presentations. The Costa Rican men however, are still seen wearing these traditional styles when working in the fields. The women typically never wear these costumes outside of the folkloric presentations. Their traditional dresses are defined by a long tiered skirt, full of colors and embellished with ribbons. The blouses are sleeveless but have wide ruffles at the neck that fall past the shoulders. Their hair is usually held back in a bun and a flower, generally Guaria Morada (the national flower), is inserted behind one ear.
Another type of clothing that is commonly worn in Costa Rica is contemporary clothing. This means the daily apparel that the Costa Ricans wear. Although the sun shines practically everyday of the year, shorts are typically not satisfactory outside of the beach resorts. If you're visiting you probably do not care, but Ticos which is what Costa Rican locals call themselves, leave them shorts for beach wear.
Ticos tend to dress very conservatively. So the most common thing you'd see them wearing around town are long pants and shirts. Mostof the citizenry wear long sleeves or jackets over their shirts as weather has sometimes become unpredictable bringing short rains in some afternoons. Men may sometimes be seen in knee-length shorts though, but again, shorter running shorts and surf shorts are saved for the beach. Dresses are worn on special occasions and are done so by the elderly people. Costa Rican clothing is also inexpensive, particularly the underwear and while the malls and shopping centers offer good deals, you will find the best bargains in downtown San Jose.