If you want directories then you don't want iPhoto. You can get the images from your camera with Image Capture (in the Applications Folder) and move them wherever you like in the Finder.
In iPhoto the concept of Directories (which is a file management concept) does not exist. Photos are imported to Events based on Date. The can be organised in Albums but really, date based organisation is very primitive for iPhoto. You can find all the photos from any day, month, year or date range (i.e. between March 3 and 14 2012) easily. It makes all those folders named for dates rather pointless.
To give you an idea of the organisation possibilities of iPhoto:
I use Events simply as big buckets of Photos: Spring 08, July - Nov 06 are typical Events in my Library. I use keywords and Smart Albums extensively. I title the pics broadly.
I keyword on a
Who
What
Where basis (The When is in the photos's Exif metadata). I also rate the pics on a 1 - 5 star basis.
Using this system I can find pretty much find any pic in my 50k library in a couple of seconds.
So, for example, I have a batch of pics titled 'Seattle 08' and a typical keywording might include: John, Anne, Landscape, mountain, trees, snow. With a rating included it's so very easy to find the best pics we took at Mount Rainier.
File -> New Smart Album
set it to 'All"
title contains Seattle
keyword is mountain
keyword is snow
rating is 5 stars
Or, want a chronological album of John from birth to today?
New Smart Album
Keyword is John
Set the View options to Sort By Date Ascending
Want only the best pics?
add Rating is greater than 4 stars
The best thing about this system is that it's dynamic. If I add 50 more pics of John to the Library tomorrow, as I keyword and rate them they are added to the Smart Album.
In the end, organisation is about finding the pics. The point is to make locating that pic or batch of pics findable fast. This system works for me.
