def go to a beginner ride. everyone's gotta start somewhere.
stay at the rear. keep your distance but still get the drafting experience, keep at least wheel length between the guy/gal in front of you. be safe, ask questions, maintain your line, have fun.

don't let ppl discourage you from what can be a wonderful and fun experience. i love group rides, from relaxed recovery rides to elbow bumping crits.

just don't show up to the fast ride and expect to keep up or them to be understanding of your inexperience. start slow, build your way up.

ps: you're already a better indoor cyclist than me. i absolutely dread trainers and can only handle being on the rollers for 60-90 minutes. i'll never ride a trainer ever again (unless its at my fitter's shop to get re-fitted )


pps: while i'll agree with some ppl that it generally does take a while to gain cycling fitness and handling capabilities, i think it's very beneficial and can help one learn certain things much quicker by going on beginner rides, even if you dropped. at the very least you can ask questions and observe others, learn safety, hand signals, verbal commands/warnings, etc.
it could even help you learn different & safer local cycling routes.