I was going to explain how hard it was to make a distinction when the speaker "feels" a difference as the nature of the street is embedded in its name, but (to my surprise) the
Academia says they must all be lowercase:
«[About the proper names of ways and urban spaces] Just like in the case of geographical names, only the proper name must be written with a capital letter, and not the generic name that goes with it, like "calle", "plaza", "avenida", "paseo", etc., which must be written in lowercase: "calle (de) Alcalá", "calle Mayor", "plaza de España", "avenida de la Ilustración", "paseo de Recoletos".
However, the generic names of ways or urban spaces that come from English, must keep their original capital letter:
Oxford Street, Quinta Avenida, Central Park, etc.»
So, I've always had this wrong, and I'm glad you asked, or I would have never known.
Here are my original examples with the red letters being the ones I would have written in uppercase.
- Estamos sobre la Gran
avenida, a cien metros de la avenida 15 de Mayo.
- El local se encuentra en la esquina de
boulevard de la Conspiración y el boulevard Héroes del Cinco de Mayo.
- Vivimos a dos calles de la Gran
vía y a unos minutos de la vía rápida Ruíz Cortínez.
- Siga derecho por la
calle Mayor y dé vuelta a la izquierda en la calle San Juan.
When I asked someone about this, they would have written all the names with capital letters; so the rule is we mustn't, but the common habit is to overuse capital letters for all the names. I guess you can choose then.