I don't know about the state that you're in, but here in CA, we have what's called the "Builders Exchange". All such public bids go through here. However, to get their periodical (and to have access to their website), you have to be a paying member. That costs a few thousand per year. There's also web-sites dedicated to having nation-wide data-bases of the same info, but again, they're pay-websites.
The only other way I know of, is you'd have to go city-to-city, going to their procurement/bids pages, etc... I've also seen how some cities advertise in the legal section of the local newspapers, but those may only trigger for certain dollar amounts where legal posting is required. Plus you'd never know what day's paper, in what city, to need to watch, etc.... So you may be stuck having to subscribe to one of the bid-watch websites.
If someone knows another way, let us know!