To elaborate on Ann's post a bit, although I have two Holga's, I only carry around one at a time. So what I do is ensure that I use the entire roll of film in the 'same' lighting conditions / environment / location / subject. This way, when I go to the lab to process my film - I only use colour slide film and I just don't have the time or darkroom to process my own film - I will know whether or not to ask the lab to push or pull the film, if necessary.

Of course, I always try to match the film I use to the lighting condition / environment / location / subject before I use the camera, so in virtually all cases I have rarely asked the lab to do anything but process the film normally. It's in cases where I don't have a variety of film to choose from and for whatever reason, the conditions changed.

If you're trying the Holga out for the first time, B&W film has more latitude than colour negative film which in turn has more latitude than colour slide film. So it may be best to try B&W film first to account for the learning curve. Get the lab to process the roll normally and see what you get.

Regards, Art.