First, postgresql comes with a GREAT tutorial, as well as three other online books totalling about 5Megs of data. Very thourough. For some reason, they don't install any of it, so you have to go to doc directory and untar the things yourself, but after that, you can put them online under a web server and point htdig at it to get a nice searchable postgresql doc set.
I have found both mysql and postgresql to be about as easy to admin and use as any database I've ever used. They are both quite stable.
If the project you're working on needs things like transactions, triggers, stored procedures, subselects (i.e. unions, intersects, excludes), or will have a lot of really funky joins (i.e. lotsa SQL92 stuff) postgresql is a pretty good choice.
If you're gonna have 100 different database users, mysql has superior security to postgresql.
But I wouldn't recommend one as being "easier" than the other. The real danger in learning one first is that when you start using the other, you will likely be using sub-optimal methods for the other database, since they work so differently. What's slow and expensive in CPU time in mysql may fly in postgresql (i.e. subselect stuff, weirdly joined tables) while the opposite is often true for things like lots of inserts (without begin;end; pairs postgresql will just SUCK at a lot of inserts, whereas mysql doesn't need begin;end; pairs since it doesn't support transactions yet anyway. well, sorta, but not well enough to compete with postgresql in a heavily transaction laden environment.)
