This again. We used to get it a lot, then it died down, now it's rearing it's head again. We've answered this many a time, and I'm sure we will many more times. For example, a quick search came up with:
http://mandalorianmercs.org/forum/index.php?topic=95116.0http://mandalorianmercs.org/forum/index.php?topic=109560.0http://mandalorianmercs.org/forum/index.php?topic=105255.0http://mandalorianmercs.org/forum/index.php?topic=40899.0But, I'm always game to have a go at this one, so lets begin!
In the Legends canon, Mandos and Force users don't get along. Too many wars and betrayals over the years has seen to that. There's a small handful of Mandalorians who own lightsabers, and mostly those are sentimental heirlooms handed down from Force sensitive or former Jedi family, or as trophies. Pre Viszla, Bardan Jusik, Venku Skirata, and Mira (arguably not a true Mandalorian and never adopted) pretty round out the list. Even then most of the owners refrain from carrying them openly. Lightsabers are a symbol of factions who we've either warred with for thousands of years, or were betrayed by, why exactly would any proud Mandalorian wish to use something like that?
From a practical standpoint, we get confused for everything from Stormtroopers, Master Chief, to Power Rangers and generic space guys as it is. Adding lightsabers to the mix and suddenly the general public can add Jedi to that list. On top of that, Lucasfilm counts on us upholding our standards to a high level that fits with the established canon.
So if you want a Mando/Jedi, go for it! Do what you like and what makes you happy, But it's not for this club.