Oh, I agree that the T-800 would be able to do quite the number the the aliens. I’d guess the aliens would do a full assault because, well, what else are they going to do? It’s not like they can shoot back. Granted the first Alien was one in a ship of eight so it made more sense for it to hide 'n grab as it matured. The ones on Archeron (LV-426) were in defense of the homeland and well outnumbered the Marines so I’d guess they’d use the same tactics against the T-800 as they do there. Hell, the things ran full on into the robotic machine guns in the shafts in Aliens which, while it doesn’t say much about their common sense, gives credit to their single mindedness and self sacrifice when defending the hive. They gave up eventually, but they were giving up on that route, not on the intruders.
No idea on what spectrum the aliens see in and I’m not even going to guess. I’m not sure how visible the aliens will be motionless against the background of hardened mucous though on whatever spectrum or even if the aliens are warm blooded. I would think a motionless alien in one of the many niches would be pretty much invisible but once they’re moving they’d lose any element of suprise. Still, a T-800 has to weigh something with its dense armor and all and I’m sure the aliens would hear it clumping around (assuming the aliens hear better than we do which is a pretty safe guess since they hunt as a lifestyle). But if the T-800 made any attempt to remain motionless and hidden, it could pull it off I’m sure.
Any idea how the aliens communicate? I never saw Ressurection and paid good money to have A:3 purged from my mind so I don’t know if it ever came up. They don’t make much noise besides screaming when they’re shot and the queen did that whole “look at the guards and they back off” number when Ripley reached the hive and made her intentions to toast the eggs clear. Phermones? Telepathy? Subsonic speech? Body language? The answer may well say how well the aliens could coordinate an attack on the T-800.
Against any single or even group of aliens, I’d give it to the T-800. Against a hive, I’d say he falls under a whole lotta acidic alien corpses. I honestly doubt the aliens leave any large jars of lye around to neutralize their acids and the “worker/warrior” types don’t have any other goal in life beyond killing things or dying in the attempt.