I was only able to lay on one side and let it "work" because I wasn't scheduled for a section at that point. I was induced and had the epidural inserted about 2pm (started trying about 1ish) and was rushed to theatre at 3:15pm. The anethetist "fiddled" with it when I arrived in theatre which made it work well enough for the section. Had he been unsuccessful with that, I would have had a GA. Lying on your side will only make the epi effective for as long as you stay on your side. I think I had a 5 minute grace when I rolled over and that was it - then I felt the contractions again... so much so I still needed the gas.
Talk to your anethetist and see what they say. They will be able to tell the probability of them being able to get the epi (or spinal) in successfully by looking at your x-ray.

HTH

MG