There's nothing wrong with trying a walk up; they don't say that you can't. However, I would be prepared to have them tell you there is no availability. The good thing is that February isn't usually a super busy time. Also, there is definitely still a possibility of snagging an ADR. Are you subscribed to the February Cancellation thread? That's helped me in the past. Also, non resort guests can make their fp+ selections at 30 days out, so if you're not at that point yet I'd suggest checking at 30 days out. Sometimes people will cancel their ADRs in favor of hard to get fp+s. Good luck!