I work for an event company in San Diego and I know that keeping within a $2000 wedding budget is no easy task! How many people are you anticipating?
Here are some websites that might be of assistance to you
Check out the city of San Diego website
http://www.sandiego.gov/park-and-recreation/general-info/bestsites.shtml
county of san diego
http://www.co.san-diego.ca.us/parks/Weddings/index.html
city of coronado
http://www.coronado.ca.us/department/division.php?fDD=13-98
city of carlsbad
http://www.carlsbadca.gov/parks/recmaps.html
The problem you're probably going to run into most is the issue of having it at night- many parks will require you to be done by dusk, although some will allow events to go on later into the night. Also, some parks do not allow alcohol, so that is something to take into consideration.
Your best bet is The Port of San Diego
http://www.portofsandiego.org/recreation/get-park-info.html
You can have alcohol (at most of their parks), and events can go until 10 pm there. I believe their permit fees are $35 for 0-100 people and $125 for 101-250 peope.
If you need any other help (catering, bartenders, linens, equipment rental, cake, flowers, etc.) contact me and I'd love to help you out!