anything with 2 wheels can also do road cycling I do long distance (100km+) on my MTB.

I can't really comment much about road bikes choices on your budget, as I don't use them, but normal gear that you'll need are as follows:
- helmet (compulsory)
- cycling shorts (very very important for cycling more than 20km)
- front and rear lights (if you cycle at nights. there's quite a number of groups who does night rides on weekdays)
- water bottle and water cage (should be able to get this for free with your bike)

optional
- gloves
- cycling computer (get one with the cadence sensor)

as for groups, it depends a lot on where you stay at. you'll need to look for a group that's close by to you so you won't need to travel halfway across the state just to join in the ride all the time (unless its a group trip to somewhere more remote)

ps. don't forget 130spf sunblock for when you cycle during the day time. unless you wish to have tan lines to wear as your badge of honor