my advice: ride on the street as much as possible. get used to it. legally you're supposed to, although even cops don't always know that. but it's best for several reasons and you should really get used to it. the better rider you become, you will definitely prefer it.
however, if it doesn't feel safe to you, there's nothing wrong with using the sidewalk imo. I have no problem doing it myself, and I'm a mega oldfag. the deal is that you're not "supposed" to be there, so whatever any peds are doing, wandering around all crazy, you have to accommodate them. within 10 feet of them, match their speed and navigate wide around them or say "excuse me" to get around. dismount if necessary, although that's rare ime. they have right of way, you're a guest.
but if no one's around, gun it. but if there's storefronts, you can't because people will exit fast and perpendicular to you, so go slow. also, the visibility of adjoining driveways is usually shit, you can get flattened by cars easily, so go slow there, too. as well as street crossings, cars are only looking for other cars in the lane they're merging with, not sidewalk in either direction. they should be, but they're not, so go slow there, also.