"I have many warm-hearted friends."
Grammatically, you can check the Speedy Guide 5.(1) and 2.(4) and think about it.
Separately, personally I am more used to describing behaviours rather than people with 热情; If I do, it would be preferably in the predicate form rather than attributive form, because of their behaviours at that moment.
Also the meaning of 热情 is not "warm-hearted" to me. People that talk to me when I'm down, send cards and flowers to me when I'm in hospital are warm-hearted but that's 亲切 not 热情. A hospitable host that always accompanies the guests, arranges lots of activities, parties, gatherings, dinners is 热情; An audience of a pop concert that screams, yells and claps hands vigorously is 热情.
I think we differ in our understanding of what the English "warm hearted" means. Your description sounds "sympathetic". When I lived in China and I had freinds who invited me to their home and shared with me, even taking me with them on a family trip, because I was out there all alone. To me that is warm hearted and the only Chinese word for such people is 热情。To me, a warm hearted person goes out of their way to include others and offers friendship and makes people feel welcome. This is 热情。