Oh well, after this...
I think I have learned some things.
There have been some coffees with no or low acidity, others with medium and others with high acidity. And finally I *think* the problem it's me.
Seems that I don't "understand" the acidity in the espresso. For me (and family & friends) the acidity is too high and not pleasant. The coffee in Spain usually have no acidity; it's sweet or, most of times, bitter, but not sour or acid; so I don't know if my "tongue" is used to taste profile.
Well, in the end, I made a post blend of:
40% Machacamarca (chocolate)
40% Brazil Facenda Inglaterra Acaia Natural (weird taste, but in the cup it tastes like a strong caramel or something like that, very very nice)
20% Malawi-Msese-Geisha-Micro-Lot (for a little acidity which balance the cup)
20% Indonesian-Sidikalang-2009 (gives a nice Banana, which tastes very nice with the machacamarca chocolate!)
As I said ,the blend(s) is very, very sweet, nice cocoa, chocolate, strong caramel, refreshing acidity or banana for the sweet tooth one.
It seems that I have to learn a lot yet...