Usually, yes, but people disagree on this. Some say "mé", others say "mè". Even native French speakers are confused! :) In the end, it doesn't really matter, because the grammar of your sentence will clear up any confusion, between "mes" and "mais", for example. http://bdl.oqlf.gouv.qc.ca/bdl/gabarit_bdl.asp?id=3074

Yes "les" sounds like the English "lay" and "des" sounds like the English "day"... That is only before a noun with a consonant. Before a vowel, you will hear the "s" and it will sound like a "z".