As much as it pains me to discourage anyone...you would be better served with a scooter. Mopeds are assloads of fun but not very reliable. The thought of riding Kirkman Rd and making my way through downtown to East Colonial sends shivers down my spine.
Peds only go like 25 to 35 mph on average unless you tweak them out...which makes them even more unreliable. I would give you a week max before you become a permanent fixture to the underside of a Lynx bus.
A good Vespa ET2, Yamaha Zuma or Aprilia will easily exceed those numbers and not leave you stranded. Finding one for 500 bucks will be a challenge though. Just stay away from the chinese built scooters!