From my experience in retail, shop workers are happy to help (at least there's something to do!). You're not seen as wasting their time, even if you don't buy anything. If you're obviously not interested in buying anything in that store, and other people are (they're busy), wait to the side while they help the "real" customers, then go right back to looking or asking questions. Chances are, they won't be so busy that you're in the way. It looks better to have people waiting than an empty store.