It certainly can't hurt to send a resume - I always recommend giving it a shot, since you never know.
The unsolicited resume submission process can be pretty brutal. Any company that is advertising on a high-traffic medium (Monster, LinkedIn, etc.) is likely to get so many submissions that they are forced into a fairly brutal accept/reject process. So you may not get much of a response, but then it can't hurt. Generally the bigger the company is, the more well known it is, and the wider it is broadcasting an open position, the more likely it is that they will be deluged.
My thought would be to give it a shot, but don't invest days and days in writing a lovingly hand-crafted cover letter. Do customize it, and keep it on topic, but don't invest vast amounts of time in a process that is likely to chew through your submission pretty quickly.