Likely not going to happen. Since prices now vary by date, specific dates make a difference. Are you going to have a car? Parking is expensive on South Beach.
What about staying either in Brickell or at the Mariota Biscayne? Both are Uber ride away.
The only thing I found on South Beach on random week days in April was the Courtyard for 80k points for 2 nights. Centrally located in a south Beach, so an option.