Bryan, one statute mile is 5300 feet (roughly, the exact number you will have to ask an American about, I never use feet and I never use miles).
An hour is 3600 seconds - exactly - that counts in metric countries too!
So take your fps, divide by 3600, multiply by 5300, and the result is mph - roughly. Or multiply by 1.47 (5300 / 3600) - roughly, even more so.
If on the other hand you want to convert knots (nautical miles per hours), then one Nm = roughly 6080 feet, so the factor becomes roughly 1.69 instead.
You might also go metric and measure speeds in m/s or km/h. Then the factor is 3.6 - not roughly, but exactly! And all your troubles would be gone.
Best regards, Preben Norholm