First of all size and age should never be a deterent to anything. I'm 5'8", 210#, 54 years of age. Do centuries, mountain bike, the whole works. Never let your age and size keep you from doing anything, ever!

OK here's the deal, what do you want to accomplish by starting to ride? Do you see this as a means to travel to the store, through the local park, cruising around the neighborhood?. You aren't really thinking about exercise, or the sport of cycling, you just want ot get out out of the house? OK, then a bolt-upright comfort bike with wide (wide not knobby - knobby tires are for trails not sidewalks or road) tires will be OK. Just remember, the more upright the bike, the heavier it is and the harder it is to push it down the street. Wide tires mean more road friction, i.e., more work. If you want to develop some speed, stay with a tire that's less than 32cc wide.

Saddle. Why wide? Wide means uncomfortable, just trust me on this. OK so you sat on your son's bike and the saddle hurt. Was probably not a good saddle and was probably a men's saddle. Look for a woman's specific saddle, like a Terry Butterfly. A normal saddle is less likely to chafe and cause problems. Check out all the threads and saddles for more information.

Gears: Of course. Helps you go up and down hills, faster and slower on flats. Get gears and learn how to use them.

Style of bike: Again depends on what you want to do. For $300 there aren't alot of choices. Get the cruiser bike and if you get strong and want to do more, you can upgrade to a real road bike. Yes, one where you have to bend forward abit. Bending forward requires the use of stomach muscles - like doing sit ups. Think of getting nice, strong stomach muscles. Not a bad thing. A bolt upright bike does nothing physically for you. It will keep you from going fast and getting stronger, but then again, if you purpose is to just get out of the house and down to the Park, it's OK.

Do you have a friend whose bike you can borrow? See if you will really stick with this before spending any money. There are lots of bikes sitting in garages purchased by people with good intentions but no motivation. Also, take a cycling friend with you down to the bike store. Doesn't hurt to bring someone along that knows a thing or two.

I think cycling is the coolest thing on earth but then again, I have a passion for riding. I'd like to see everyone get the passion but I'm dreaming. If there's anyway I can cause a spark in you, I'm willing to help out in anyway!