They voted to become a state in 2012 and Congress ignored it.
No, they didn't. The fact of the matter is, that the people of Puerto Rico have never shown any majority preference for a change to any particular status. To settle this issue correctly, any multiple-choice referendum would have to allow for a ranking of the different options, after which, ideally, a second binary referendum should be held to confirm the winner (if it's a change). My guess is that, by this procedure, the status quo (or something close to that) would still win out at the moment.
The fact remains that the result of the vote was in support of statehood, or at least dramatically more supportive of statehood than in the past regardless of whatever technical arguments you have, and Congress' response has been total indifference. That's ridic.
