I voted "maybe." Which is to say Saudi Arabia being a reliable ally in the Middle East all comes down to our money and their mood.
"Every time something really bad happens, people cry out for safety, and the government answers by taking rights away from good people." - Penn Jillette.
No, they are not.
Saudi Arabia is not an ally but merely a good business partner. And for that, even this is getting worse and worse.
Saudi Arabia is where radical Islamic ideology was born. Look up Wahabism and then tell me we should be allies with these people.