First, have your air conditioner serviced and your filter replaced. A shortage of coolant means a shortage of air conditioning.
Second, close your air vents downstairs, this will help to get more cool air upstairs. For more boost upstairs, have your handyman install a duct fan ($34 at Home Depot). They look like this:
Third, get an attic fan installed. Most of the townhouse heat is sun radiation on the roof. The attic air gets much hotter than outside air. Have a handyman install an attic fan to exhaust that hot air out. Before I got the fan, I had some success by keeping the upstairs bedroom doors closed.
Fourth, have your handyman seal up any air leaks from doors, window, electric sockets, floor boards and attic panels.
Fifth, to save money get an electronic thermostat that lets you schedule your cooling. This way, the house can stay at 80+ degrees while you are away at work, and then be programmed down to 75 degrees at 5pm when you return.
Sixth -- Window Air Conditioners are an eyesore and are discouraged. If you have exhausted all your other options, you can apply for a temporary waiver from WHFHA to intall one in a window facing the back yard, while you arrange to upgrade your central air unit.
By the way, if you are getting a new central air unit, have the installer create an extra long duct to the large intake vent in the living room. This was done on my new unit, and the fan noise in my living room is very much reduced.
