I haven't had any problem with PostgreSQL and my spanish char set so far. But I have noticed the problem you are pointing out with acspg.
I dived through the code and noticed that the problem came from the line
regsub -all ' "$string" '' result
in the DoubleApos function defined in the ad-utilities.tcl.preload file. I changed it with
set result [string map {' ''} $string]
and now it seems to work. (??)
I tried the regsub in my tclsh interpreter and it had no problem, but it does have inside aolserver.
Hope this helps.