I am thinking of getting a bike, but having not cycled since I was on a girl's bike 25 years ago, I don't know where to start, other than my local cycle shop, which is about as friendly as a pack of piranhas if you're a female beginner. So can anyone advise me, prior to going to the bike shop, so I don't sound like a complete dunce?

I'm not planning on cycling anywhere other than around my local park, for fitness, so maybe 20-40 miles per week absolute maximum, no off-road, no commuting.

My guess would be a very basic road bike would be the way to go. Also, I'm 5'7" with regular legs and torso, but really short arms - any recommendations of make/model? And finally - can I get something for $500 or less?

I'd appreciate any advice.
Thanks,
Helen