Table partitioning

I have a rather large and slow table in Postgresql 9.1. I'm thinking of partitioning it by months, but I don't like the idea of creating and dropping tables all the time.

I'm thinking of simply creating 12 child tables, in which the check condition will be, for example, date_part('month'', time_arrived) = 1 (or 2 for February, 3 for March etc.).

I'll just be deleting records rather than dropping tables, the same way I do in my current setup. I delete a week's worth every time.

So, I have two questions.

First, is constraint exclusion going to work with that kind of condition? I mean, if my WHERE clause says something like "time_arrived >= '2013-04-05' and time_arrived < '2013-04-17'", will it be able to tell that date_part("month",time_arrived) for all the records is 4, and therefore avoid selecting from any partitions other than the april one?

Second, when I delete (not drop!) from the mother table, are records deleted automatically from the child tables or do I need to create rules/triggers for that?

TIA,
Herouth