Well if you are nervous, then just stay with the small lakes until you feel comfortable.
... which provides an immediate look at the water conditions rather than masking them behind the calm of a harbor.'Sail off a beach' ...
Not every beginning sailor has ready access to a small lake, many learn to sail on the ocean. The size of the body of water really isn't relevant, as said before it is the weather thats important. 5 knots of wind on Lake Superior is going to be more enjoyable for a beginner than 20 knots on the local duck pond.
Florida lakes are better for a steady breeze, but weather can change it quickly. I've had two thunderheads build above my head and was not sure which one was going to hit me with unmanageable winds. (While sitting becalmed!)"..."Close to shore" in that kind of lake is "crazy wind". The shore terrain can really play havoc with the wind. It is puffy, and the direction changes constantly - hard to sail in..."