I have had CD for more than 15 years, and have had more than 6 surgeries. I have had to be on steroids so much during my CD lifetime, that now, at the age of 32, I have severe osteoporsis, so I would just like to preface this response with the warning that while steroids can certainly help you to get over a flare, just please be careful on relying on them for too long, or on a high dose.
Also, I understand that you say that your last colonoscopy was in 2003, and that you really can't afford to pay for another, but honestly, 2003 was six years ago, and that is an awfully long time, and a lot could have happened to your intestines/colon during that time, especially if you have had any surgery, as you could have developed adhesions or scar tissue.
You could always go to the ER at a hospital for uninsured people, and if you just told them that you were new to the area and had not had a chance to find a new GI doctor, perhaps the ER doctor would prescibe the prednisone until you could "find a new GI and get in to see them soon". They may even perform the colonoscopy or at the least a CT scan to make sure you aren't obstructed or something serious.
It sounds like your bloodwork has indicated that you have some infection going on because your white cell count is elevated. Did the bloodwork include a C Reactive Protein (CRP) count? That measures the amount of inflammation in your body.
Have you attempted to contact the hospital/facility where you would be having the colonoscopy performed by your GI to inquire about any programs that you could apply for that would either provide you with financial assistance, arrange for discounted rate, or if you qualify for a free colonoscopy? Or perhaps, they would work out a payment plan. One other thing I would try is to contact the CCFA chapter office in your area and ask them if they have any resources or ideas that may be able to help you in your situation. They would definately understand that time is of the essence in getting your symptoms and/or flare under control ASAP.
I definately would express your concerns to your current GI doctor calmly and cafefully, as you certainly don't want to get black-balled or labeled a "problem child". Unfortunately, that is a very real concern, especially when all of the GI docs know and talk to each other (despite that being unethical and most likely illegal, it happens all the time). If after having a frank and calm discussion with him/her about your situation, and they are still not assisting you in in any way to try and figure out a way to get the treatment or tests that you really need, despite the obvious fact that your CD is flaring, I would find a different GI doctor. But don't leave the original doctor on a bad note, or "burn a bridge" because you are with Kaiser. I probably wouldn't even tell the doctor that you were "firing" them, I would just make an appointment with a different doctor under your plan. Every doctor should absolutely be sensitive to their patient's financial situation (especially in today's economic climate), and they should be doing whatever they possibly can to get you treated ASAP.
I hope that eveything works out and that you are able to get the appropriate treatment ASAP, so your flare doesn't lead to something more significant.