Staying motivated is a big issue with me too. I love cycling, but sometimes it's hard to roll out of bed early enough to beat the heat and the traffic. The best I've found way to keep it up is to have someone to ride with one or two times a week, because that way I have someone relying on me to get out of bed. It's too easy to turn off the alarm(s) (I end up setting seven different ones every night) if I'm going out alone. If you don't know anyone who rides, recruit a friend. Since I'm 17 I had to try that option since I don't have any readily available buddies to ride with.

Also, when you're first starting out, pick out some routes you like doing and stay with those. Try not to concentrate on dropping pounds so much at first, but developing good habits. It's way easier to get out and ride if you're not dreading enormous hills or a painfully fast pace.

Welcome back to the cycling world though, eh? The most important part is to have fun while you're at it.