Como el agua de mayo
 

I think in means with great anticipation. Lo espero como el agua de mayo.
Am I right?

Yes, you're right. This is a proverb (?, I don't know the correct word for "refrán"). Usually it is said without the article: "lo espero como agua de mayo", but I've seen it written in both ways. May water is good for agriculture, so it is said in the sense of waiting for something with a great desire. :)

Gracias
proverb=refrán

There's a slight difference beteween "refrán" and "proverbio" in Spain, although the RAE doesn't distinguis between them. A "proverbio" is more serious, even more philosophical than a "refrán", which comes from the popular wisdom. We can talk about Chinese, Arabian, Jews, etc. proverbs, for instance. We know some author from proverbs, but none from "refranes". For example:

Proverbio: El que teme sufrir, ya sufre el temor (proverbio chino)
Refrán: Agua que no has de beber, déjala correr.

Yes, "proberbios", al igual que las "citas" (quotes) usually are "intelligent sentences", with know origin or not.
Examples:
The virtuous man is driven by responsibility, the non-virtuous man is driven by profit: Confucius
Resistance is Futile: The Borg
When a man sits with a pretty girl for an hour, it seems like a minute. But let him sit on a hot stove for a minute and it's longer than any hour. That's relativity. ~ Albert Einstein
anonymous
A Camel is a Horse designed by committee
In God we trust. The rest must pay cash. (US Depression saying.)
Open minds and empty heads are not the same.
Wise men speak because they have something to say, fools speak because they have to say something.


"modismos" are a sentence you use to say other thing
Examples: ask Rusty for this point :D :D
"To be two faced", "all talk and no action"
"refranes/dichos", are anonimous intelligent sentences but with a "country/rustic/popular" point of view. For me, the main point is that "refranes" are practical, and "proverbios" are more philosophic
Examples of refranes
"quien a buen arbol se arrima buena sombra le cobija" (If you lean to a good tree you will be protected by a good shadow )
"Más vale pájaro en mano que ciento volando" (A bird in the hand is worth two in the bush)

For example, this last one, as "proverbio" should be something like " If you have something secure, don't play it double or nothing"


Saludos :D

Muy buenos ejemplos, Sosia.

Lo puedes decir más alto, pero no más claro.

Por cierto, ¿qué tipo de frase sería ésta? No es un refrán ni un proverbio. Supongo que será un "dicho".