The answer to the teleport question actually depends on how you are achieving the teleport effect. The teleport ability does not require line of sight, however as wild gotten pointed out you do need line of sight to your targets when you cast a spell. The incantation spell called teleport involves targeting both the creature in question and the destination zone, so you need to be able to see both. However the enchantments divine intervention does not require you to have line of sight to the destination, nor does teleport trap. The teleport abilities of blue gremlin and gray wraith also do not require line of sight.
Basically, unless it says you have to have line of sight or have to target your destination or something else too that effect, teleport does not itself require you to see the zone you are going to and you may indeed go through a wall.
