It's traditional to treat temporary hit points like hit points, but there's a great big caveat: there isn't a set tradition for how you treat hit points.
First, temporary hit points. This comes from the SRD:
Certain effects give a character temporary hit points. When a character gains temporary hit points, note his current hit point total. When the temporary hit points go away the character’s hit points drop to his current hit point total. If the character’s hit points are below his current hit point total at that time, all the temporary hit points have already been lost and the character’s hit point total does not drop further.
When temporary hit points are lost, they cannot be restored as real hit points can be, even by magic.
You'll note that nowhere in there does it state that you are not permitted to know how many temporary hit points you have left. The temporary hit points are simply added to your current hit points, and when you lose hit points temporary hit points are lost first.
You should also note that it says nowhere that you are entitled to know what your current hit point total is.
There's no hard and fast rule for who holds character sheets, makes notes, tracks hit points, or rolls the dice. Maybe the DM only runs the monsters, and you run your character's sheet. Maybe the DM has your full character sheet and you have an index card with your abilities on one side and equipment on the other. Maybe there are two DM's, one who runs monsters, and another who controls character sheets and makes rolls for the party.
I've been in games where all of the above occurred (not at the same time, thankfully), and I've DM'd using even more unusual methods of tracking stats (the award for most difficult to track was "feed everything into a computer so not even I know what will happen next"). All are equally valid, if more or less difficult and/or fun. Ultimately, then, the tradition that's going to be most important in your case is the one your gaming group follows.
That said, if you're trying to avoid meta gaming, your character wouldn't know the numeric value of an attack that damaged their temporary hit points any more than they would know how many hit points a dagger would deal... but, just like anyone can tell an orc with a great axe deals more pain than a peasant with a dagger, your character can tell when they've been hit harder or softer, even if the hit only impacted their temporary hit points. It'll be up to your DM (probably- see caveat above) to describe the damage in a way that's meaningful for you, whether that happens to be telling you that you lose 9 temporary hit points or that your psychic ward pulses from the force of the mace smashing against it, but holds firm.