I've now made my poster in 3 obscene PDF files:
1. all the vector objects remain as vectors in respective layers, all text is actual text object with included font, all raster images uncompressed: 88 MB total, takes a while to render the vector map
2. everything cast into one big raster image at 300 DPI: 23 MB, loads fairly quickly on my machine
3. everything cast into one big raster image at twice the resolution: 58 MB, Firefox cannot display it, Apple Preview takes half a minute to load the visible canvas but if you move around the PDF at all it takes another half a minute to fully load
OMG what have I created 
Which of these do ya think the print shop can actually make?
I think 2 is a sure bet, I'll be disappointed if they can't handle that one. 1 may work depending on what PDF viewer they use. 3 no way, I think the windows machines they got to control the print machines are 10 years old with 8 GB of RAM at this point