Hundreds of Seattle area concrete mixer drivers who have been on strike for more than three months will begin returning to work Monday, though they still have not reached a deal with their employers. Teamsters Local 174 said Friday afternoon that all of the more than 300 drivers on strike have “offered an unconditional return to work starting on Monday.” “This won’t stop the negotiations. It will just stop people thinking we’re to blame and we’re the bad guys,” said Brett Gallagher, a mixer driver and member of the bargaining committee. “We have a lot of mud to get done and lot of people to ge…