Hi Lara S!
Just make sure that you are not out alone at night and don't walk the beach after sunset. It is pretty easy to connect with other travelers here, especially if you happen to be staying in a hotel or B & B. If you are the type of person that can easily meet people, then you will have no problem.
Be aware of your surroundings and if you are uncomfortable, then get out of the situation.....really, if you are in SJ, you know the drill. Keep your belongings safe and if you don't want to lose it, don't bring it with you....except for your passport of course!!! Santa Teresa is a pretty friendly place!