Originally Posted by TrojanHorse

I'll add one of my favorite one-way routes. The general idea is that you park at a metrolink station and return via metrolink, so this is a one-way trip from Anaheim / Corona (or Riverside if you're extra motivated).

The hillier route: https://ridewithgps.com/routes/15777777 (83 miles, 4300 feet, 8 miles on I-5 to bypass the marine base, features Imperial/Cannon, Santiago Canyon, Modjeska and Live Oak for the climby bits)

The flatter variant: https://ridewithgps.com/routes/14476152 (81 miles, 2800 feet, this route also goes through the marine base - feel free to mix and match, a variety of OC bike paths on this route)

There are a bunch of restaurants and places to eat in the general area near the metrolink station in Oceanside. Check the schedules but the weekend train pass is $10 for all day and the Riverside train departs O-side at 2:50 and there is usually a later option as well.