Just a few tips, I think putting out 50 on a Friday late afternoon is going to be your best bet. Code enforcement which are the local officials that govern such a thing normally take these signs down between Monday and Friday early.
I say put them up Friday afternoon because the agency employees are off the streets and getting ready to wrap up there week. Majority of the city workers are off during the weekend. This will give you the highest exposure for your signs before they are taken down.
Another tip is to bring a step latter and hammer stapler. The higher you put them the harder and less likely they will be taken down.
One thing you must know, they will be taken down!!! It is just a matter of time. So these low cost ads are something that you must know will be thrown away. But they are cheap, I can buy them locally for less than $0.90 sign and stand.
Oh and I'm sorry, the other thing you must know, these are ILLEGAL in most US Cities, I cannot speak for outside of the US. The best way around this is if they can't find you they can't fine you. Make sure your domain name is privately reg'd and you put no telephone number that can lead back to your name.
Hmmm this would make a good blog post....coming soon