I'm having lateral release surgery on my knee. There has been no MRI or xray, should I be concerned by that?

Yes. You should be concerned. Lateral release is done for a very specific reason for patella symptoms. There should be at least a x-ray or ct scan done to evaluate patella alignment. Also, an MRI may show articulate cartilage damage which may affect the outcome of the surgery.
Yes and no. While it is true that some experienced Doctors can diagnose patello-femoral disease with a good physical examination, most agree that imaging to confirm the physical findings would be prudent. In addition, lateral release surgery should be done as a last resort after all other therapies such as medication, exercise, physical therapy and others have been tried and have proven to be unsuccessful.