Could I consider a facelift considering that I have Psoriatic Arthritis and take Methotrexate?

I have never had a problem with patients on Methotrexate. It would be best if your psoriasis is under good control before you had the surgery. If you do not have any other medical problems I don't think it will cause a problem provided you go to a well trained competent surgeon. Good luck.

Yes, you can consider having a facelift.  There are several studies in the orthopedic surgery literature that show no increase in surgical site infection in methotrexate users, at least in rheumatoid arthritis.  Best to discuss with your rheumatologist, though.

Without knowing your age, seeing photos of you, or examining you in person, it is difficult to answer your question with any certainly.  I would say that if your face exhibits the classic signs of aging (excess of your upper eyelids, puffiness of the lower eyelids, deepening of your nasolabial folds, jowl formation, neck laxity), you would need preoperative testing and a letter of medical clearance from you internist before having surgery. If your internist cleared you, then you could move forward with your surgery and could look forward to a beautiful result.