I was off the bike with a broken foot for a similar amount of time, and finally got back on the track last weekend.

After I was finally back on the bike I went up north for some work, and brought a bike with me. The only real ride I could do (due to location) was a 30 miler out and back with a couple thousand feet of climbing. When I got back to civilization, I was hitting the highest averages I've ever had on my daily loop.

That being said, climbing worked as great conditioning (for me), and got pretty much all of the lost muscle mass back fairly rapidly.