Please confirm: three of you with a budget of PHP1,000 to PHP1,500 per person, and all of you are sharing a room -- so that's a budget of PHP3,000 to PHP4,500 per night for the room?
If that's your budget, then you have a whole lot of options since PHP3,000 to PHP4,500 per night is more or less the median range of hotel rates in Boracay.
El Centro charges PHP3,300 for their deluxe rooms that can accommodate 3 people. More or less the same with Boracay Beach Chalet.. These two resorts are right at Station 2, so you'll be in the middle of the action. These two are also pretty much what you said you're looking for: pretty basic and right by the beach.
If you want someplace quieter, try checking out resorts in Station 3.
If you want someplace even cheaper, you could go for hotels that aren't by the beach, like Boracay Holiday. It's a two-minute walk from the beachfront, but you do get a lower rate than comparable hotels that are along the beach.
Hope this helps!