There are many small canyons in the city of San Diego. This web site tells about many of these canyons: http://www.sandiego.gov/park-and-recreation/parks/oscp/maps.shtml.
Some have hiking trails but many remain in their natural state. There are volunteer groups who work to preserve these canyons.
closest national park to san diego?
San Diego Padres
San Diego is the closest, with the San Ysidro and Otay Mesa communities right at the US-Mexico border.
The closest with a baseball team would be San Diego, California. Its local team is the San Diego Padres.
The closest hotel to the Sea World Way entrance to the park is the Holiday Inn Express San Diego, 3950 Jupiter St, San Diego, CA, 92110.
550 miles
Check Mapquest.com
The closest found is - San Diego Civic Light Opera 1549 El Prado San Diego, CA 92101
From San Diego to Evansville, Indiana (the closest part of Indiana to San Diego), is about 29 hours driving, not including stops.
Los Angeles
Yuma
The closest Mexican beach to San Diego is Playas de Tijuana. It's about 25 miles from downtown San Diego.