I'll be moving to Grand County (Granby) in early March and I was wondering if there were any others out there, and where and when you ride. Or, if noone who lives there rides, do any of you guys from Denver ever head out there for some weekend rides?

Grand County is better known as a mountain biking area. Granby is surrounded by mountains. That being said, there are some highways in the area but the shoulders are minimal at best. I don't think I'm brave enough to ride on Hwy 34 or 40. There are a few less-busy county roads there as well but many of those end up in dirt or gravel.

Do yourself a favor and make sure the mtb is ready to roll. You could ride it for days on end and never ride the same trail twice.

Can I use your message to convince my wife I need to replace my 10 year old mountain bike? Actually, I'm pretty sure she's already aware of what needs to be purchased for us to stay active up there.
I could have sworn I read somewhere that riding 34 to Grand Lake and even to Estes Park was a pretty popular route (which led me to believe it was safe and not uncommon to see riders on it.) I'm sure I'll find some other crazy soul to ride the road with me up there when we're not on the trails, but I imagine what you've said is right, and that most of the LBS in Fraser, Winter Park, etc. are going to be 90% mountain bike supportive.

Hwy 34 over Trail Ridge Road to Estes is a good route. I was thinking more in the other directions. Trust me when I say that a good long-travel full-suspension mountain bike would fit the bill nicely.

If you're into this type of thing, there is a Red Cross fundraising event every June called the Fat Tire Classic. It's up in Winter Park. I volunteer there every year as a course marshal. There will be as much mtb riding as you can handle and free lodging and food. Let me know if you're interested and I'll send you some info. It would be a great way to meet some cyclists (albeit the fat tire variety) and support a great cause.

It's certainly true that Grand County is well known for mountain biking and rightly so. However, there are several options on the road as well, especially if you're willing to drive a little.

You can ride Hwy 40 from Granby towards Kremmling and beyond. The traffic is much better after you get past the turn off to Grand Lake/ RMNP. In between Granby and Hot Sulphur Springs you can take CO 125 north towards Rand/Walden. There's not a lot of room, but there's not much traffic here either.

If you want to drive and start in Kremmling, you could do Gore, Muddy and even Rabbit Ears passes. On over towards Yampa, there's miles of picturesque two lane with mild traffic.

I suggest you pick up a copy of Road Biking Colorado by Michael Seeberg. It has all these routes and more in detail. Be sure to stop in Rocky Mt Roastery/Totally Wired Cycles in Fraser. Best beans anywhere.

Are there any scheduled/organized rides on Trail Ridge Road from Grand Lake to Estes Park or vice-versa? Unless someone tells me it's suicidal with summer traffic, I expect this route will be a major part of my triathlon training this summer.
I've been up here for 2 weeks and I'm drooling at all of the potential for road riding. Most of the road here have wider shoulders than I'm used to for snow removal and the others seem to have low traffic and/or bike friendly people. I'm sure this will change somewhat with the summer tourists, but I'm still excited. Made it on my bike once so far and only made it 7 miles before the elevation/cold kicked my ass into reality.

I don't know of any organized rides up there. Since some of it is within RMNP, that makes organized rides a little harder.

In the summer, if you're up there early enough you shouldn't have much trouble with traffic. I don't think I'd want to be up there at 1pm on a Saturday.