Some general thoughts and questions.
Since the Squid Men do not speak, can they hear? maiking the Squid Men deaf might add a disadvantage a non-psionic character can exploit.
About the read surface thoughts ability, doe sthis mean that someone who has very good control over there thoughts, and maybe can act in a zen-like manner, could sneak up on them?
Does read surface thoughts work on non-sentients? I'd suggest it does not, 'cause it might be nice to sick dogs on 'em.
I'm thinking that the Squid Men use their eyesight and Read Surface Thoughts to "see" their environment. They might use a servant to "hear" by hearing through their servants surface thoughts. If deaf, they might be fascinated or repelled (or both) by music.
Another advantage for non-psionic PCs is Squid Men might also have a general distrust of computers and sophiticated electronic gear in general, potnetially making their security systems weaker. Instead, they may rely on their servants as guards.