1. Welcome.
2. Ask you dad what the hard limit is on the budget.
3. Don't even think about BD at this time- you know nothing about bikes. If your dad did, I'm sure he would've influenced your list.
4. Forget Wal-mart and other big box stores. They are cheap initially, but will cost as much (if not more) as an entry level bike from the LBS in the long run.
5. Best to rely on the knowledge base a LBS provides. If budget constraints really dictate otherwise, the next best thing is to find a bicycle coop. You get most of the same LBS knowledge, combined with learning your own wrenching skills, at a reduced price.
6. Based upon your name and height, I'm guessing you're female, so you might want to consider contacting a Mod about joining the mythical 'Women's sub Forum'. It exists, but shielded from the general population, so doesn't show on the main index.