The island of Margarita has a wide range of restaurants and local eating houses to cater for all budgets and styles. It is customary for a 10% service charge to be added to your bill. While your server may receive a small portion of this, it is not a tip for your server. In most cases part of it goes to the "house" for breakage and incidentals, with maybe a small portion split between the help. If you received good service, it is customary to tip your server.
Some go as far as rewarding the bartender separately when eating out and their service was exceptional. Don't be surprised if you order a mixed drink and the bartender brings the bottle of liquor, glasses of ice and mixer to your table. A bartender pouring a triple shot of liquor for the price of a single is not unusual.