You can get one off with a cheap screwdriver and a hammer, inserting the driver into the slots on the lockring and tapping lightly on the screwdriver.

The problem using this method is not so much getting it off but getting it properly adjusted when you put it back on. Since your adjustable cup is older, it could be any one of three methods:

1) The adjustable cup might be slotted.

2) The adjustable cup may have a wrench flat, usually 25mm.

3) The adjustable cup may have pin holes.

Which is it? Really, you need a lockring wrench and the proper spanner for your type of BB cup. You're in the DC area; you should at least be able to get a lockring wrench (the Hozan c-205 is a good all around one, though there are others). The pin spanner for option #3 on the adjustable cup should also be gettable and cheap; Park makes one.

Buying the tools (assuming #3) should be about 20-25$; cheaper than shop work and will save you hassles in the future. If the bike a rider, you'll want to overhaul the BB with some frequency (1-2 times a year).