A 5,000 BTU window air conditioner usually uses around 4.7 AMPS when running but can go higher when starting up.
With that said I have a 5,000 BTU window air conditioner in my shop plugged into a power strip and it has been just fine for the last 3 summers.
A typical cheap power strip you buy at walmart can handle up to 15 amps so as long as you're within the 15 amp rating then you should be safe using the power strip.