"Smooth Jazz" is more of a radio format term, not neccessarily a type of music (jazz).
There are just as many (if not more) types of jazz than there are rock so it's really hard to guide you. You really need to sample some stuff. I don't think 95% of people starting out into jazz would ever even "get" Metheny, Mehldau, Coltane etc. and could give up quite easily.
Most of the crap they play on the "smooth jazz" radio stations is actually R & B, Adult Contemp stuff anyways. Many of the jazz "purists" disregard a lot of the more contemporary stuff but it is a lot easier to listen to and to start with in the many jazz genres.
Starting out I'd recommend stuff like....(This stuff is easy to listen to but it's decent music with good musicianship)
Rippingtons...."Curves Ahead", "Black Diamond", "Wildcard", etc.
Spyro Gyra...."The Deep End", "Wrapped in a Dream"(latest)....yes Beckenstein on sax is terrific and Scott Ambush is one of the true masters on bass.
Acoustic Alchemy...."Aart", "Beautiful Game"
Ken Navarro....."Island Life"
Feel a little more daring??
Yellowjackets..."Time Squared", "Blue Hats", "Mint Jam"
Dave Weckl Band...."Transition", "Multiplicity", "Perpetual Motion"
Pat Metheny Group..."The Way Up", "Speaking of Now", "Road to You (live)" etc, etc....
Caribbean Jazz Project..."Here and Now (live)"
Joshua Redman...."Momentum"
Al Dimeola..."Orange and Blue"
This isn't even a surface scratch. There is tons of stuff out there but unfortunately none of it is played on radio. You could go to Amazon and read more on these releases, get samples or pick a couple up to get started on a long journey. Good luck.