I'm from Mexico! From your list I love Leandro, Marco and Mateo (that's on my list :D).
Here are some other names I love:
It's hard for me to say how easy those would be for a non-spanish speaker, since it's my first language, but from my experience those are all doable. Javier and Joaquin might be the most challenging because of the J, but I know a Javier and Joaquin who live in the US and don't seem to have issues. They go by Javi (HA-vee) and Quin (keen).
I love Marco!
Other suggestions - these names were all on our baby names list! My hubby is Hispanic as well.
I like Marco!! But the Marco I know is from Croatia and lives in Canada though! Lol
Nvm it is spelt Marko. But I like it better with a 'c' anyway! ha