An Air Carrier Captain refused a MGGT revised departure clearance while in position for takeoff because in IMC. The revised route would have been off airways near terrain. The cleared altitude was below the MSA and off the engine out procedure routing.

Narrative

We were given permission to line up and wait. In position on Runway 01; Tower gave us takeoff clearance followed by departure instructions. The instructions were to climb out on the 345 radial and climb to 8000 FT. I refused the clearance and taxied down the runway and exited. We had to get an amendment to our minimum takeoff fuel since we were going to be below 23;600 LBS. Dispatch amended it to 22;600 LBS. We were now number three for departure. I refused the clearance for several reasons: 1) We would have been IMC during our climb out. 2) The note on the general info page requirements about accepting radar vectors inside of ten miles. It states; 'Flights must be established on a published route or segment of an approach procedure by 10 nm.' That same reasoning should apply to departures that we should be on a published route or segment as well. 3) The Controller cleared us to depart Runway 01 and climb out on the 345 radial; which is west of the engine out procedure and a climb limit of 8;000 FT. That is not a published airway or segment of a procedure. That is 1;200 FT below the terrain in that segment of the MSA quadrant; 10;200 FT. This ensures 1;000 FT clearance from the terrain within 25 miles of AUR vortac. We were then cleared to takeoff and fly the published departure procedure. After departing and during our climb out we arrived over; or close to the mountain ridge in question and it was about five minutes +/-. We mentioned this to departure and tried to explain why we refused the clearance and they did not agree with us. This has occurred several times departing MGGT. If the Controllers are going to give us something other than what we have been cleared or expect to do; then give it to us earlier than in position on the active runway. Also; it should be a published airway for terrain reasons.