Hi,
Combining the two (cycling and weights) is something i've been doing over the last 2-3 months.
Although cycling is my main thing, I don't particularly want the typical cyclist look, and want to maintain (or even build) muscle on my upper body. I don't bother working my legs, as the cycling is good enough for that. Though I have considered trying squats to build a bit of thigh power for fast rides.
What i've found is that when doing around 100 miles a week, my upper body workout is often a struggle, compared to before I started cycling. Maybe this is something to do with the lack of bloody flow around my arms?
Before working out i've started warming up my arms for 5 minutes. Just warm-up exercises. And it does seem to help. If I don't, I often find I have cold hands, which is an indication of a lack of blood flow.
I've just bought a weight bench to start bench pressing as well. So that should be interesting...
Anyway, in answer to your post, I think its a good idea to start doing a few weights. Just bare in mind, muscle is heavy, so if you build up too much you will probably find your cycling more of a struggle, and if you're getting serious into it, it might not be the best idea.
All depends just how serious you want to get into cycling.