Are you sure about the no grouping with players over 20? When you join a BG your in a raid group with 21-24s. In addition, I remember a TI user asking if he can make a trial and run himself from his own DK, someone told him he could.
Now, about getting to out lands, I know the sw > blasted lands portal reqs 58 but does the blasted lands > outlands portal itself have a req? Perhaps you can manually run to blasted. What about summons, can trial accs accept instance stone/warlock/guild summons.
Wait a sec, someone made a thread about timbermaw Exalted, level 20 can't grind furbolgs by the,self, they must have grped with someone to run them.