Answer:
I don't have an exact answer, but I can tell you what I know. "al" = "a"+"el", so you just need to know if you need a definite article "el" before the noun or not. al is basically contraction of a el. Ir a bar would be go to bar. Which is grammatically incorrect.
Correct English version is go to the bar or go to a bar.
Thus correct Spanish version is ir al bar or ir a un bar.
In case of proper names (places, people), you don't usually prepend them with article (there are few exceptions). Thus the correct form is to say vamos a España.
I hope this helps, and have a great day!