I'm 5'9 too
I can't imagine only weighing 135 though. I'd probably look like a stick. My favorite weight is between 140-145; it's very maintainable for me and with the weight training, I look pretty good.
I've just started getting into cycling recently. I bought a crappy old mountain bike at a yard sale and I've been going on longish rides (15-20 miles) once a week or so. I live in a rural area with a very active biking community and there are some beautiful places to ride with gentle hills. I wear my HRM so I can count the rides as exercise
I find it *much* easier to burn 500-800 calories on my bike on a 90 minute ride than I do to burn 300 running on the treadmill. It takes a lot longer, but it's lower intensity. (I am somehow unable to get my heart rate up to 80% on the bike, unless I'm hauling *** up a hill. Running I can always settle at 80%).
Anyway, I'm loving it but I need to get a road bike. The mountain bike isn't great for these long rides. Trouble is that road bikes are soooooo spendy. I'm in the research phase at the moment