Thought I'd post an update to my original here.
I decided to exchange the glasses I purchased from 39DollarGlasses
(number 3 in first post). Their customer service has been great! They
agreed to exchange two single lens glasses for the one pair of
bifocals! I was able to handle all of this over the phone and expect
to have the replacement glasses next week. Yeah!
The glasses from Discount-Eyeglasses (number 4 in first post) arrived
last week directly from Hong Kong in a nice, hard shell case.
Unfortunately, I did NOT notice when I ordered them that the frames
and lenses are HUGE. They appear to be for someone with a head the
size of a gorilla! Makes me wonder why their website didn't post some
type of disclaimer or refuse to complete the order when they saw that
my PD was only 61. I contacted Discount-Eyeglasses and received an
email from Kam (the owner?) who offered to exchange them for a
replacement fee of $29 plus $6 to ship! I worte back to say that I
was interested in learning more about the exchange, but now that I
think about it, I doubt I will do so for that price. It would be
easier to buy another pair from another online vendor. I think I'll
keep the HUGE pair to show people how important it is to pay attention
to the sizes when ordering!