We've stayed at the Stratosphere the last few times we were there and loved it. The rooms are okay- clean and the beds are decent. We were hardly ever in our rooms anyway. The last time we stayed we got the room for something like $60 a night. Go to their website and sign up for their emails. They send out promo emails all the time with great rates.
The bus does go to downtown. That's how we went to Freemont and back to the strip, so that's definitely an option.