If you want an affordable place that is incredibly well-located, stay at Jenn's! We spent 4 nights in her condo, and it was convenient and perfectly suitable.
The reports about the noisy birds are true. The A/C unit isn't loud enough to drown them out, and we also brought a white noise machine which didn't fully cancel the noise. Once I put a pillow over my ear, though, it was perfectly silent -- so bring earplugs and you'll be fine!
It's one of those places where the price and the location are so stellar that they outweigh any inconvenient noises that might keep you up. Nearby, check out the countless bars and restaurants. I especially recommend South Shore Tiki Bar for drinks and the Kihei Caffe for breakfast (get the pork fried rice with eggs over easy -- we had it every single day!). There are also snorkel shops, bike rentals, and beautiful views everywhere.
Finally: We rented a car and used it every day to get to different beaches, but there were buses going up and down the street that I'm sure it'd be quite accessible by public transportation.