From two legs to two wheels

I'm considering taking up a new physical hobby...cycling. Now I'm not what you would call a cyclist. I didn't even learn how to ride a bike until I was 7. Thanks to my friend Whitney who let me practice on her bike until I could ride it on my own.  Since then I've had a couple of bikes including my pretty pink cruiser than is collecting dust in our garage.  It got a lot of use when we lived in Ft. Collins, but since we moved and there is not Old Town to ride to it's been sadly neglected.

Anyway, I've been thinking about doing a sprint tri for which I'd need a bike other than my cruiser.  Yesterday Josh and I stopped at a shop in Longmont so that I could try out a road bike.  I was really nervous about the super skinny wheels.  Once I was on and actually pedaling it wasn't so bad.  Of course it will take some getting use to but I think I can do it especially the whole leaning over and the weird braking. I will definitely not be keeping up with Josh anytime soon or using toe clips. The last thing I need to to have my feet stuck to the pedals. I'd be the person at the stop light like this:

I'm not sure if I'm going to love it so we're going to keep our eyes peeled for a used bike. No sense in spending $1000 on a bike until I know whether or not I like riding.  It will be great crosstraining exercise.

Any tips for a newbie cyclist?

By the way, running is not going great. Last week I ran twice for a total of 7 miles. I was going to run 7 on Sunday but I took a few steps and the shooting pain returned. Luckily I have PT tomorrow.  If I can't run three times a week in the next couple of weeks I'm going to have to seriously consider dropping from the full marathon to the half.  Booooooo.