for 150 US$ it's hard to find good hotels in Venice. Probably by now you found an hotel in Mestre on the mainland...
In case you still have to book your accommodation, I could recommend to contact an agency that rent apartments also for few days that operates in Venice. They come to pick you up and give you advices on your trip. It is a cheaper but very smart way of travelling if you find the right company. I've been renting before with Truly Venice and I can say only good things about them... check out www.truly-venice.com