-Do they have special holidays that they celebrate with dance?
I could not find any specials holidays. But fanatics of Argentine Tango should not miss the annual Buenos Aires Tango Festival which takes place between February and March. There are masses of performances all over the city and lots of opportunities to learn a few steps of the most famous dance in Argentina.
-What other art forms do they practice that might have influenced dance?
Tango has a complex history.
Tango was the first couple dance ever seen in Europe that involved improvisation. Before the arrival of Tango, couple dance was sequence based, with every couple on the floor dancing the same steps at the same time.

-Do they have religious traditions that would incorporate dance?
As far as I can tell from my studies, there are no religious traditions that would incorporate the dance. Tango began in the underclasses, born on the outskirts of Buenos Aires city, where men frequented brothels and bars where the only women present were prostitutes. Perhaps the physical liberation between prostitute and punter was the driving force behind the development of Tango in Argentina. In the 1880's socially accepted male-female relations were formal and the idea of a close embrace was unheard of, especially in public.

How do the citizens come to learn this form?
The dance took longer than 9 months to learn.
Tango was surprisingly uniform across the whole of the city.
The young man who was starting to notice the attractions of young women had little option but to learn to dance the Tango. Once he was considered to be good enough at dancing the woman's part he would be allowed to