Well i cant speak spanish but I done an assignment on the same topic so heres what i had..
The main point that you need to consider is that illegal graffiti obviously has a lot of cons but all other types are just artistic expressions...
Cons:
form of vandilism (usually on public property)
can be visually unattractive
Decreases the value (usually of houses surrounded by graffiti)
Costs the city millions to clean up
Pros:
In controlled environments can be a geat way of artists showing their work
Graffiti walls and workshops have been used to keep youth off the streets
Gives artists a sense of territory.
Hope this helps!