Directions will very frequently depend on gestures or on your hearer's knowledge of local geography, but it's easy enough to imagine circumstances in which the first sentence would be intelligible. For instance, if you're standing in a corridor leading to the back of the building you direct your hearer down that corridor to its end out front of the Seminar Hall—that is, outside the hall facing its entrance— the bathroom is now on your hearer's left, either on the same corridor or down another corridor leading to the left:
SH or SH
____/back\___ __________/ \________
| out front | back
/ of SH | out front of SH
←BR | ___BR↓__ ______
| | \ | |
| | | |
| | | |
| | | |
ADDED: ColleenV points out that another possibility is “Go back the way you came from, until you get to the front of the seminar hall, then turn left”.
Your second sentence is a bit different. The word original suggests that what is meant is that the neon sign, which had been removed or replaced, is now back (restored) in its original position out front of the bar—that is, outside the bar on its front wall.