I bought the Dragon Valley world. I put it onto my computer Why can't I move to Dragon Valley? Where the hell are the dragons?

You need to be more specific about how you "put it onto your computer" and what happens in-game when you try to move there. Does it say it's installed in the launcher? Is it in your Installed Worlds folder? Can you create a new save game with Dragon Valley or does it not appear in the menu?

I don't own Dragon Valley, but this page explains how dragons work (obtain the eggs from Buy Mode).

I'm sorry. I should have been more specific.

You have to create Dragon Valley by selecting a new game, then choosing it. As for the dragons, you have to actually buy the egg from by mode and then wait for it to hatch

No need to apologize. It's just that it's impossible to tell what went wrong without knowing what happened. Downloading and installing the store worlds can be confusing. If you got it on a disc, you still need to log on to thesims3.com and input the purchase code in order to actually be able to play it. After you put in the code, go under "Purchase History" and Dragon Valley should be there, along with a button to install it for real.

Edit: Lord St.Croix, I think it's also possible to move between towns using the phone as of patch 1.55. You can choose from the options "move within this neighborhood" and "move to a new neighborhood." Your sims will lose any relationships with people outside the household, but you can choose to pack or sell furniture and the ages/relationships between sims in the household will be preserved.

EA did place some of the dragon eggs in various lots, some of the houses have them too. Still, if all else fails, get them from BuyDebug.

You can find them in the minor pets section too, if you have pets installed