Selling townhouse I am renting is this a breach of the lease by the landlord?

It depends on what state you live in.
Also when does you lease end? Many owners put their rentals up for sale not wanting or expecting them to close until the end of your lease.
They are allowed (sorry) to have the house shown to agents and prospective buyers, with limitations of when and how often usually, but that goes by state law too.

Selling townhouse I am renting is this a breach of the lease by the landlord?

Is the sale subject to your lease? If so, the buyer would become your landlord and no, it wouldn't be a breach. You would continue to occupy the premises for the remaining term of the lease.

This assumes, of course, that there is nothing in the lease prohibiting the present landlord from assigning his or her interest.

t/y I live in fla. Lease ends last day of April 2012

Unless your lease specifically prohibits it (unlikely) then it is not a breach. The new owner will have to honor your lease (but not extend it).

Do you want out? Its possible the new owners want to move in and would be willing to buy you out.