In every lease there are implied covenants of habitability and quiet enjoyment.  Habitability has to do with the premises (including the common areas outside) being in a safe and sanitary condition.  You didn't mention it, but I imagine that the grounds are less than hygienic right now.  More to the point of your case, quiet enjoyment has to do with just that - being able to quietly enjoy your rental unit.  Obviously you can't do that given the circumstances.  You again need to contact your manager and make them aware of your legal rights (preferably in writing - keep a copy).  If they still fail to remedy the situation, you may have grounds to terminate your lease.  However, before taking any action (termination, withholding rent, etc) you need to consult directly with a tenant's right organization or an attorney who specializes in landlord/tenant matters.  Failing to follow the law could end up costing you.