Right, many companies rely on applicants assuming they'll spend the money for a background check, when in fact, many don't. My advice is to lie if you think they'll look askance at your record. Either they check, and you don't get the job, or they don't check, and you do get the job. If you're honest about it up front, it's likely the same outcome as "they check." As I say, this can depend on what type of company you're going to apply to - are they a buttoned-down corporate type of place, or rather hip? Is security a big concern for the employer? What are your convictions about? Drug convictions will be less of a problem than theft or violence convictions.
I once had to take a pre-employment "lie-detector" test, and was asked about drugs. When I answered that I had used them, he asked which ones. Since he wouldn't take "pretty much all of them" for an answer, I had to sit and list every drug I'd ever tried. It was a very long list. I got the job, and my test results got big laughs with my new bosses and colleagues. They were, (rightly), concerned about theft, not how I spent my free time. So, if it's only a bunch of drug-related misdemeanors, (or felonies), take heart!
I now have a job where a very dim view is taken of this sort of thing, and I never say a word about it, even though I have some arrests and minor convictions. It's not come back to bite me.