This is from the US Department of Health and Human Services:
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8. What if you have a pre-existing condition?
Before passage of the Health Insurance Portability and Accountability Act (HIPAA) in 1997, people had to worry about health insurance coverage for preexisting conditions like diabetes, heart disease, or cancer. If you changed jobs and had to change insurers, you might not have been able to get some of your care covered because of the preexisting condition exclusion.
Today, HIPAA helps to assure continued coverage for employees and their dependents, regardless of preexisting conditions. Insurers can impose only a 12-month waiting period for any preexisting condition that has been diagnosed or treated within the preceding 6 months. As long as you have maintained continuous coverage without a break of more than 63 days, your prior health insurance coverage will be credited toward the preexisting condition exclusion period.
If you have had group health coverage for at least 1 year and you change jobs and health plans, your new plan can't impose another preexisting condition exclusion period. If you have never been covered by an employer's group plan and you start a new job that offers such a plan, you may be subject to a 12-month preexisting condition waiting period. Federal law also makes it easier for you to get individual insurance under certain situations. You may, however, have to pay a higher premium for individual insurance if you have a preexisting condition.
If you have not had coverage previously and you are unable to get insurance on your own, you should check with your State insurance commissioner to see if your State has a high-risk pool (described previously in this booklet). You can find the phone number for your State insurance commissioner in the blue pages of your local phone book.
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So, you should be able to get insurance anywhere you want if you fit the timeline requirements. Make sure you get a proof of coverage letter from your current insurance company before you cancel.