SoCal, I highly recommend "Baja Fish Tacos" for fish tacos, they have 3 types of fish tacos: Grilled, Blackened (Cajun) and Ensenada style (beer batter), they also have Shrimp quesadillas (with green or red sauce, not spicy), you'll think twice before going back to Rubio's.
If you want to have a very healthy fast food option, you can order a salad with your choice of meat on top: fish (any of the 3 types already mentioned) or Carne asada, no carbs at all!