StubHub is pretty reliable and eBay is usually. I just bought 2 sets of tickets off eBay about a month ago and both came in a timely matter. You can't really get screwed over from eBay because you can usually just get your money back as long as you pay with PayPal.
When I went to the opener a few days ago, there were plenty of scalpers walking around the stadium and also a ton of cops, who didn't seem to bother with them. If you don't know what game you plan on going to, that's probably your best source of tickets when you get there instead of getting a seat in Row X on the tier level from the booth. If you know what game ahead of time and plan a trip to the stadium around that, go for StubHub or eBay.