San Diego's EarthFair is in Balboa Park. Transit routes that serve Balboa Park --
3 - bus between Downtown and Hillcrest - southbound on 4th Ave, northbound on 5th (1 or 2 blocks west of Balboa Park)
7 - bus from Downtown via Park Blvd or from La Mesa via El Cajon Blvd
215 - Express Bus from Downtown via Park Blvd or from SDSU via El Cajon Blvd
From South County - take Blue Line trolley to City College
From East County - take Orange Line trolley to City College
From North County inland - take 235 bus to Boulevard Transit Center, then 7 or 215 bus to the park
From North County coastal - take the Coaster to Santa Fe Depot, then Blue or Orange to City College, or 215 bus direct to Balboa Park
From City College, walk 4 blocks north or take a bus to the park