I’d like to be able to switch to Spanish from time to time. I selected the keyboard but it doesn’t stay selected (by the flags). I also went into system preferences and added Mexican Spanish. But I don’t have a clue how to get it going for any length of time.
Thanks
Huh. I’m honestly not sure.
But on those infrequent occasions when I need to type in Spanish, I just keep using the English QWERTY I’m used to (a different layout would slow me down), and use standard keyboard shortcuts for special characters.
Many of the shortcuts are some version of Option + whatever the special character looks like (sometimes followed by a letter, if you’re adding an accent). Others are Option + most commonly used letter with the accent + the letter.
So:
¡ = Option + 1
¿ = Option + Shift + 1
é = Option + e + e
í = Option + e + i (I’ve no idea why this accent is Option + e)
ü = Option + u + u
ñ = Option + n +n
Then I just set my spellcheck to Spanish. 
Muhlenberg College has a handy cheat sheet.
Terrific! Thanks, Amy! I use to have the f keys do the same thing on my old Mac.
I noticed last night that on a Mac Pages can handle several languages without the underlining!
Eng, Spa, French, German, Italian. Amazing!
Option+e is how you get all the accent marks, so á é í ó ú are option-e followed by a, e, i, o, and u. Very consistent!
¿ is Option + Shift + / (or Option + ?) Option + Shift + 1 is ⁄ the “fraction slash”
Terrific and for the exclamation point? ¡ LOL!. Got it! thank you.
Thanks for catching the error! My fingers got ahead of my brain.
I agree that Option + e for the accent is very consistent. It just seems like an odd choice. I’d have gone with Option + ‘ (which kind of looks like an accent), followed by the letter. I think it’s a little weird to have to type an e to get an accent on an o.
At least it’s consistent and easy to remember. 
Option e gets the accent that points up to the right because somebody thought that was the most common accent on an e. That’s true in French. é
Umlaut is option u probably because umlaut starts with u. In my experience o gets an umlaut more than u ¯_(ツ)_/¯ nōel
Option ! And ? Get the inverted ones. That’s nice and easy.
Tilde accent is option n and not option tilde because ñ is popular. It is a bit weird since option back tick plus character gets grave accent. à
I certainly type all my limited French on the standard English keyboard. I have no idea how good the Spanish/Mexican keyboard is, and what is more often used by native Spanish speakers.
Good luck.