I would recommend Dieters, an independent in downtown San Diego. Hoehn Porsche is located in Carlsbad alongside the 805 freeway. Sorry, I don't know of anyone closer to Escondido.
Carlsbad to Escondido is less than 10 miles. From Escondido, just take the Rte-78 West towards Oceanside, then it's a quick 3 miles South on the I-5. Hoehn Porsche is right off of Palomar Airport Rd