Hi man, now I live busking with the violin in my town, Palermo, Sicily, Italy. I have been one year in Spain, but just Barcerlona, Zaragoza and Bilbao as city where I have been busking.
And I can tell U that is everywhere the same:

- choose the right place (not so rich part of the city, nor so touristic, the right stay in the middle)
- try to look people on the eyes, and try to smile as much as possible, or anyway change often the facial expressivity.
- If U want to ask people if they would like to share with U their money, try to be the much more funny and polite, anyway U will find your way by the experience.

That's all I suppose

I hope U the best

Some word in spanish:
- hola cielito lindo. Hello clear sky ( to a beutifl girl)
- Buenos dia Senora (have a good day Madame)
- Buenos dia (Hola) Jefe (hallo Boss)
- No hablo espanol, hablo angles. (This U understand)

Spanish, the most of all, doesn't speak english, so would be better to learn it, also on internet for free (interacitive-spanish I think)

I hope u the best, Antonio