No accent on the Spanish o, or.

From street and store signs we can learn a lot about the language we wish to acquire. But... watch out because all that glitters is not gold (no es oro todo lo que reluce.)
Madrid is always full of tourists, foreign and domestic, who meander streets and alleys in search of sights to take pictures of. They also eat and read restaurants billboards where they can see:
"Ensalada ó pepitoria. / Cafe ó té. / Vino ó cerveza." almost always with the accent on the "o", or.
These small things are importante because they show the cultural background of the enterprise, almost always run by native speakers.
Native speakers are dangerous people. Beware!
There is no need to accentuate the "o" in Spanish, not even between figures: 5 o 6. Notice the size of the "o." If it were five hundred and six, the zero would be noticeable: 5 0 6. 
5 o 6 = 5 or six.
5 0 6 = 506.
That simple.
O entra o sal = either come in or go out. O...o = either... or.