Just my 2c..
(I'm starting to think that should be my user name by now)
If money's tight, and let's be honest, isn't it usually for most of us anyway, then compromise is often in order.
If you can get free (or at least cheap) rubber, and the choice is this or no riding, then what's the problem?
A free new tyre from a known manufacturer will beat a balding, canvass showing tyre from one of the big three every time. At least for regular street use.
Ask yourself, are you planning on riding at 10/10ths in tricky conditions trying to get the elbow down? or just going for the occasional blip around the local twisties and doing a bit of commuting?
As long as you keep in mind that the rubber you're on is not premium grade race track stuff, and as long as you take it relatively easy while you "feel" the new tire out, you should have little to be concerned about if you're an even half competent rider.
It's up to you, and how you ride.
It's pretty common knowledge that putting on brand new rubber *any brand* and trying to go straight out and start scraping the pegs is a recipe for disaster. Just use the same common sense with an "unknown" brand and who know's, you might just find that this brand works better for you anyway.
(though pilot powers do take some beating IMHO)
In any case, if you are prepared to forego the knee dragging, you'll still be able to get around a lot more safely than you could with knackered tires while saving for the rubber you really want.
For what it's worth, Maxxis don't make complete crap nor do Continental so it's not like they're going to just shred on you for no good reason.* Lot's of bikes run on these tires or they wouldn't be manufacturing them.
*That good reason being trying to run as hard as you might with a better quality, more expensive tire.
Their tires may not be as good as the others but it's not like their just going to explode or fall to bits like something made by say, "Super Lucky Golden Dragon "or "Cleatus' Round Rubbers"
All you have to do is remember that you get's what you pays for and ride accordingly. Then when you've got the cash, go and get the rubber you really want / deserve.
Stay upright dude!