I would go if I had nothing else to do, and the parks were closed.
On our last trip we stayed at BLT and took the monorail to the Poly and GF just to see them. We have never stayed at either.
But if you use the monorail just be careful that you're back to where you want to be before the stop running the monorail!
But if you're coming from the MK, it'll take you about 10-15 minutes to get to the GF, since it'll make stops at CR and the Poly first. Just make sure that you are getting on the resort monorail and not the one that will take you to the TTC.
The monorail stops running about an hour after the park closes...so they should be safe. Also...both monorail lines, running from MK, stop at the TTC. The Express Monorail runs between MK and TTC, with no other stops. The Resort Monorail runs thus...MK, CR, TTC, Polynesian, GF, MK. If you take the monorail from MK to the GF, it will take about 20 mins. It's about 25 mins for a complete loop...so it's a bit less to the GF.
The boat may be faster. If you see the GF/Polynesian boat, either at the dock or coming in across from the Polynesian, take the boat. But, if you see it heading to the GF or from the GF to Polynesian, you may be better off taking the monorail.
Do I think you should see the GF lobby?? If that sort of thing is of interest to you, then sure. It makes for a nice break in the park day...if you want to eat lunch, out of the park, then take the monorail and get off at the CR and check it out, then get back on and go to the Polynesian. Get a bite to eat at Captain Cooks at the Polynesian and then get back on the monorail and head to the GF...check it out and go back to the MK. It will take about 90 mins, but you could do it in less time if you don't dilly dally.
If you just want to check out the GF, then plan on 45 mins..travel time and looking time.
