mollykins, this will likely come as little surprise to the staff at the tower. You don't have to be face-to-face with anyone (although at smaller airports you can go to any of the ground staff who will facilitate a direct contact with the tower or else relay the information to you) because once you are there you can telephone them and explain the request, via an operator if necessary or if it is a bigger airport then even any of the airline operations offices should be able to get the information for you. There is in fact another way - if you have an airband receiver you can listen in to communications between the tower and aircraft preparing to leave (this may be a separate wavelength from the general air traffic frequency). It is a rule that at the start of communications the tower announces the barometric pressure to the cockpit contact. No need to feel silly - that does not get you anywhere in this or anything else. Getting an official pressure reading at a proper point of measurement is always going to be much more accurate than if you interpolate from a remote reading (or have someone do it for you). But perhaps inaccuracy does not matter if the barometer to be set is itself not accurate.