I haven't trained a Yorkie alone before, so this is my first time and this is what I learned:
About peeing outside: at first Chibi (my furbaby) would not go outside when he was 3 months, he was a little scared so I just brought the pad with me and left it in the grass, nothing happened, but after taking him outside several times, eventually he went outside. (It turned out that the pad outside made no difference.) Then I praised him well for maybe a minute and gave him a small doggie treat. After repeating this several times eventually he would go outside, however he still uses the pads when he is indoors. When he goes on the floor we don't say anything, just wipe it up then wipe the area with dilute bleach(it removes the thiols, or smelly part of the pee-pee), and wipe dry so he can't lick it. When he goes on the pad, and we catch him going, we praise him well while he's in the act, and give him a treat when he's done. At 6 months he has started to hold it longer, about 5 hours. Personnally, I think it's ok to let him go on the pads when you cannot be home, just try to bring him out on a regular schedule(if possible!). After all the are so little!
Chibi is getting better, but we're not there yet, sometimes he mistakes the rug for the wee-wee pad, but we're going to try some methods that were posted here on Yorkie talk!