Playing a scoundrel in my friends EoE game, he's mostly the group face, so I was thinking to continue in that vein, picking up politico as specilization number 2, does this make sense, or is there another, better specialization for an interpersonal focused character?

How are they going to be interacting? If it is more mercantile based Trader might be better. Really depends on the form of social interaction anticipated to be most likely used.

It's really hard to say what's "better" in this circumstance for your character. It depends whether you want to focus heavily on one Social skill or be better at several, and what your combat role has been to this point: if you're a good shot you may not want to spend actions on Inspiring Rhetoric/Scathing Tirade (or maybe you don't want to shoot and would prefer the leader/buffer/assistant angle that those Talents provide).

My human scoundrel is well into all three Smuggler trees (Scoundrel, Pilot and Thief). He's quite the well-rounded cad...

I think it comes down to where you see your character going. I started off as an assassin because my character's back story was that a Falleen gangster offered to smuggle him off of Zolan if he acted as the gangster's personal bounty hunter/assassin. Teeg broke away from the gangster when he realized he was spinning his wheels and not getting any closer to going home and leading a Clawdite uprising against the Zolanders. Since his ambition is to do so, his first dedication was spent on bumping his presence and saving enough XP to buy into Mercenary Soldier for the leadership skills. Teeg is already pretty devastating with the shooty so it made sense to improve up his social side. I'll probably work on keeping him limited to those two specs until the BH splatbook comes out. Depending on how long our campaign goes, I could see him branching out to Politico too, if he's able to successfully lead his Clawdite brothers and sisters to freedom.
TL;DR: Your character will tell you what your next spec should be.