KBUF viewing
On the north side there is 2 good locations. The one mentioned, old Flying Tigers/now Mercy Flight. Aero Dr, next to runway 23 tunnel, turn onto Amherst Villa Rd.
Also another northside location for rwy 23 is Aero Dr, north on S Youngs Rd, right Lawrence Bell Dr. near where ILS beam crosses Lawrence Bell
On the south/east side, near intersection of Genesee St and Holtz Dr, for rwy 32. There are a few spots like Holiday Inn and a gas station, which don't usually bother you parked there short term.
On south/west side, 3901 Genesee St. for rwy 5. This is Make-A-Wish Foundation. It used to be NY Thruway offices. Then it was usually wide open with no problem parking there. Now the parking lot is filled more with company vehicles and workers cars. Not sure if it's a problem now.
On west side, off Cayuga Dr. near US Post Office. There you'll see the big cargo aircraft and any charters for sports teams.
Hope this helps