As others have said, I fold that bottom 20% - 30%, even giving the BB a walk, unless I have a good read and think they'll fold to a modest raise. Otherwise I miss the flop too often, then I have to get away with something (out of position) to win.
I also rarely limp in SB; for me it's typically raise or fold. The 'discount' of limping in the small blind used to be really attractive and I'd limp with almost any two cards in this spot, but I figured out that it's a terrible play for me - the outcomes are too often bad.