I've walked 5/6 caminos with a pre-existing condition. I never bothered with private health insurance and made sure my E11 card, or whatever it is called now, was up to date. I only ever had occasion to use it on one trip, after a bad fall just outside Valencia. I soldiered on for over 6 weeks with a constantly infected shin, stopping every 3/4 days at a local clinic (like the old cottage hospitals in the UK) to get it cleaned and re-dressed. Usually with a letter/note from the previous one, telling the next one, what they had done. I was amazed at how quick it all was and how fantastic the treatment was. Miles better than what would have happened in the UK. Names of insurance companies that do pre-existing conditions that I know of are Staysure, All Clear, Aventi & Puffin Insurance. Good luck