Keep in mind that the deal between StubHub and the Angels ended this year. Although people can still choose to sell tickets there, the season seat holders can no longer post tickets there directly from their Angels account. Unfortunately, since they are making a transition this year, whatever system they will have replacing that is not up yet.
I wouldn't expect a game against a division opponent to sell out, even on a Friday. You may want to buy fairly early, though, since you want premium seats. Before buying from a reseller, check to see what you can get from the box office. Usually the selection is quite good if you know what game you want and get online the day single tickets go on sale. Like a lot of teams, the Angels haven't actually announced when the tickets *will* go on sale... last year it was on March 3rd. Like most teams, they normally go on sale on a Saturday... but I've seen teams not even announce it until a week before. I'd check the official Angels site once a week.
In general, the rows start at A then work up... after Z comes AA and BB. On the field level I think it varies, though... they try to keep rows the same across each aisle and the spot where the seating starts can change from section to section. The Angels have started doing special pricing for the first row on the field... refer to the seating chart. When it says "109 field" that's just the section name... the 100s are referred to as "field" even if the actual seat is in the back row of the section. You'll also see "MVP", "All-Star", and "Box" for sections that are progressively farther away from home plate.
By the way, take a look at the Club level seats (300s). I don't recall offhand if they will be out of your price range, but they are just high up enough to actually give a better view of the game then when you're on the field. In addition they are luxury seats so they have more padding and include in-seat food service. (Oh... didn't notice at first that this was already mentioned... still the best spot to sit if you can afford the cost of the tickets.)