EOM.
Yes, you can upgrade from SMF 1.1.x to SMF 2 Beta. Just download the SMF 2 Beta 'Large Upgrade' package from the download site (http://download.simplemachines.org/), upload it into your smf directory and then extract all of the files. Don't forget that you should make a backup first.
Also, please note that custom themes and mods probably may not work with SMF 2 Beta, they will also require reinstallation.
Documentation:
Upgrade SMF (http://docs.simplemachines.org/index.php?board=3.0;sort=subject)
Thank you very much for the info.