ahw01,,
Unless the law has changed recently (and I don't have a FAR/AIM 2003 handy - but you can check the FAA website) you are right in that there is no minimum time to convert ASEL to AMEL. What you might consider is doing your FAA IR first and that way you can convert onto the multi engine and invoke your instrument privileges at the same time.
FAA rules allow a fair amount of simulator time to be credited for flight training.
Depending on where you go, in the USA all manner of interesting flights (such as across to the Bahamas, into Las Vegas or New Orleans etc) can be done whilst under instruction towards your rating