cubs are good planes and fly nice, but a .20 cub might be a handful for a beginner. I would look into picking up a standard trainer and finding a dedicated field to learn in (with instructors)

flying a glow powered plane isn't recommended in a public park as they have a high potential for damage if something happens.

I would check out any local clubs and see what they can hook you up with. since you fly already (helis) and have some airplane experience you should learn real quick, so if a local club has a "club trainer" that might be all you need to get going.

but again I wouldn't recommend a small cub as a first plane as even though they fly nice, they have some quirks that might make a small one too unsteady for a beginner.