I have written numerous articles on this topic ( on Salsa Forums and Salsa/Jive )so I will just say this.
There are numerous " styles " in music AND dance in Salsa .
It depends largely on how the music is written .
ALL Mambo/ Salsa is based upon Clave and Son rhythms . Depending on which rhythm the music is composed in ( SON.. Guajira, Montuno, Guaganco etc. ) it will affect the interpretation of the dance .
Purists say that ALL Salsa is mambo but.... NOT all mambo is salsa .
It is a very complex dance with multi layers of interlaced rhythms to allow for just about all beats to be interpreted at some point .
Many teachers now teach breaking on "1"..but for the wrong reasons ( expediency )... if one knows the difference, then that in and of its self is not a bad thing .It takes many months of intensive partner work to establish the use of "2".. sometimes called dancing on Clave ( not literally )
If you insist on developing a more authentic approach, then the correct method to commence is to break backwards on "2"..(mans right foot )technically known as " call and response " . The dance is based on the African Yambu and Orisha forms, hence the start is important .
If you start into salsa, your options are generally NY, LA, Power2 , Cuban and Puerto Rican styles . Most dance LA on "1", PR on "1 and 3 " the rest are on "2" .
Be very careful of the videos on show.. many have very poor technique and mis information.
I have a vid. from a w/shop I recently did in London, its brief, but might help...http://uk.youtube.com/watch?v=PAzmP645a38