Go to Extraordinary Desserts, for dessert and coffee obviously but they alse have great sandwiches, salads and cheese platters. It is located on Union St., downtown/ little italy.
http://www.extraordinarydesserts.com/
I would bring your rain gear. It is raining right now and is suppose to rain over next weekend.
The zoo/balboa park are a taxi or bus ride away. Not too far from downtown. It is possible your hotel will have a shuttle.