Sounds like if the PCs are working over N and the printer isn't, would mean that the printer isn't setting the N mode correctly. The router is probably set up correcty. After you switch to the G and N mode, do you power cycle the printer after and see if it picks up the N mode? I should at least pick up the G connection.
If, it's working over Mixed modes then I would probably leave it there.
And lets be realistic for a minute. Do printers really need High speed connections to send a print job? I work in the printer industry and ya it's nice to have wireless for printer however a high speed connection isn't really needed and most print jobs are fairly small in size and are mostly processed on the PC first, then sent to the printer for actual printing.
Unless your doing volume printing or working with large picture files alot, having a printer connect at G or even B modes won't impact print performance. Once the printer has been handed the job, it's up to the printer to get it done, not the connection.