Hi, as a rheumatoid arthritis sufferer of some years I will say the following. Both flavours of arthritis benefit from a warmer and dryer climate, my condition is classed as advanced and is kept in check with weekly self injections of methotrexate followed by a folic acid tablet two days later. I require regular blood checks (my rheumatoid blood factor is 80, whereas a normal read would be circa 20), I take regular exercise and try to keep my weight down, and my blood pressure on the high side of normal. Your hubby would be well advised to get himself registered with the rheumatoligy department of a Spanish hospital, the average GP (in my experience) knows next to nothing about arthritis, I was within circa 18 months of losing the use of my right hand when they finally referred me to a top teaching hospital, they were superb.
I wonder if your husband's current rheumatoligist could refer him to his/her equivelant in Spain, and remember when taking out travel insurance to declare his condition and medications, I use Flexicover as their on-line medical screening is quick and easy, plus they are not expensive.
Good luck to you..