What kind of reed do you prefer for saxophone?
I have heard mixed reviews about vandoren and Rico...

What do you prefer?

I prefer Vandoren reeds. (I have nothing against Rico's).

Vandoreen is very popular and used by musicians.

What is the reed numbers suitable for a beginner to the tenor and alto? What if the beginner is an adult with or without an experience on playing band instrument?

Try starting out on a 2.5 or 3..those are pretty soft and easier to produce a tone...

Make sure when you buy the reed you specify to the guy who is selling them to you, that you need TENOR sax reeds or ALTO sax reeds since they are different. You might wanna start off on RICO Size 2.5 or 3 reeds, they are cheaper and still decent reeds. The music store guy should help you out to make sure you get what you need