Can Valium be taken sublingually

Short answer - Yes for Instant release pills, No for extended release.

Yes you can, however; it will affect you a little differently. First, it is likely that it will give a stronger effect, due to a lack of what is called "first-pass metabolization" by the liver (some anatomical differences from swallowing it versus sublingual, insufflation, or rectal administration). Second, it is likely to last a shorter period of time, an hour or two less. Third, while the pill is bound with glucose and other sugars normally, amphetamine itself is rather unpleasant tasting.