Here's my advice:
1) Go to a shop and get fitted. You're going to want to buy used to get a decent bike in your price range and so it's imperative that, if buying from CL or eBay, you know exactly what size you need
2) Ask about last year's models. It may be that the shop has some left over and will give a discount that's enough to make it worth the extra $$.
3) If you do decide to buy elsewhere, support the shop by buying your gear there. Shorts/Helmet/Gloves/etc.
4) Don't get anything "less" than Shimano 105 or SRAM Apex components.
5) Have fun! My first road bike was a used Trek 2.1 from eBay. It had a few hundred miles on it but looked brand new. 105 components and paid just under $1000.
Everything said here. But I would definitely lean towards buying it at the shop. I got my Specialized at Rassy's and at the end of the day, they gave me shoes half off, free pedals, free helmet and first tune up. You won't get that online.
I would also suggest getting a cross bike with an extra set of tires. It will open you up to gravel and off road rides because if you catch the bug, which is hard not to do, you will want to ride anywhere and anything.
I would also suggest AGAINST a hybrid. Almost everyone I know that's gotten one has regretted it quickly and traded theirs in.
Another place to check is the Des Moines Bicycle Collective. They have some really good used bikes sometime at really good prices... plus it's a great organization.
Also, don't be intimmidated by clip in pedals and shoes. It's a lot easier than it looks and makes the ride much more enjoyable.
And a Taco/Steak/Beer ride NEEDS to happen