Although most of Costa Rica is safe, petty crime and robberies committed against tourists are endemic. San José is known for its pickpockets, so never carry a wallet in your back pocket. A woman should keep a tight grip on her purse (keep it tucked under your arm). Thieves also target gold chains, cameras and video cameras, prominent jewelry, and nice sunglasses. Be sure not to leave valuables unsecured in your hotel room. Given the high rate of stolen passports in Costa Rica, mostly as collateral damage in a typical pickpocketing or room robbery, it is recommended that, whenever possible, leave your passport in a hotel safe, and travel with a photocopy of the pertinent pages. Don't park a car on the street in Costa Rica, especially in San José; plenty of public parking lots are around the city.
Rental cars generally stick out and are easily spotted by thieves. Don't leave anything of value in a car parked on the street, not even for a moment. Be wary of solicitous strangers who stop to help you change a tire or take you to a service station. Although most are truly good Samaritans, there have been reports of thieves preying on roadside breakdowns.
Public inter-city buses are also frequent targets of stealthy thieves. Never check your bags into the hold of a bus. If this can't be avoided, keep your eye on what leaves the hold. If you put your bags in an overhead rack, be sure you can see the bags at all times. Try not to fall asleep.
Single women should use common sense and take precaution, especially after dark. I don't recommend that single women walk alone anywhere at night, especially on seemingly deserted beaches, or dark uncrowded streets.
