Escondido is only 30 miles from downtown SD (where the airport is.) Even during peak rush hour it's only a 60 minute commute. Normally it's a standard 30 - 40 minute drive.
That being said there is bus service between downtown and Escondido. Looks like busses depart every 15 minutes. Cost is only $2.50 one way and the route takes an hour. One would need to Uber from the airport to Santa Fe depot downtown (will take 10-15 min for no more than 10 bucks.) Here's the link for the OP.
https://www.sdmts.com/sites/all/themes/mts/templates/sdg/pdf/235.pdf