IFR means you must maintain 1,000 feet above the nearest obstacle within 5nm of your track. There is absolutely nothing to prevent you from descending to the altitude you mentioned to clear cloud whilst still complying with IFR. Best to get a radar service although bear in mind that the controller will usually inform you that you remain responsible for your own terrain clearance at all times.
Obviously, you need to know your position at all times and plan in advance.