The busing transports to Mendenhall Glacier puts you in close enough range to have a satisfying view......otherwise.......when you get there (via bus) you will see a water fall in the distance. If able to do some minor climbing it's possible to hike there--which will get you even closer to the glacier. Haven't done the hike; plan to in near future.
Scroll to top of this page and click on Search option; type in key words. If you schedule through any ship excursion pay close attention to time. If you do this independently you still give attention to timing but I believe you have more options of buses to return to docks. Depends on who/what company brings you there....and, of course, how many ships in Juneau that day--with most passengers wanting to view Mendenhall.
It's a good idea to write your bus number/company name down on a small pad or something as there are many buses coming and going. Buses are not allowed to stay in drop off point. Forest Service enforces rule to prevent vehicle congestion.....so driver gives a time that he/she will be back for passengers with fair (but friendly) warning not to be tardy.