I'm also an engineer. I've worked for a few top-ranked ENR firms and ALL of them required pre-employment drug screen. If you are working for a small business, chances are they won't waste the money, they'll just try to really get a feel for you in the interview.

The only time I've been faced with randoms is when you get on the construction side of things. If you take a field/project engineer position you're likely to have randoms. Also, if you're working on a government contract you'll likely have randoms, even at a very small firm (its always part of federal contracts).

I spent a year having randoms. Look into this fake urine product:

Quick Fix

There's tons of good information about it in the drug-testing section of this site. I got high every night during randoms. Quick Fix worked without any problems, although you may be nervous the first time you tried it.

But things are a little more laid back up here than TX. I worked at a small firm where the boss smoked. I didn't find out until after I left, but I think he sensed that I did and was still a good worker and liked me for it. Its not a big deal, just make sure you don't tell people you work with. It works the same here as it does down there. Your medical card will offer you absolutely ZERO protection from being let go. Good luck!