What good would a fence do? We've just recently found tunnels. (Actually, the Israelis have had to deal with tunnels, too. ) And if we blocked the land borders, with either fences or tunnel blocks, we'd still have to deal with the coasts. "Securing our borders" is a slogan that is meaningless. And I haven't even mentioned access by air.
We do need guest workers. It's a real shame that we got rid of regulated guest worker programs and wound up with unregulated illegal immigrants. There are many legitimate arguments about how we get back to a regulated guest worker program, but pretending that we don't need one is folly.
You just answered your own question. The Israelis have had to deal with tunnels, and yet their fence has proven enormously successful at reducing terrorist attacks. Conclusion: Tunnelling is not nearly as effective a means of entry as being able to walk across unfenced or poorly fenced surface.
What I'd really have to ask of you at this point is if you're looking for something that's guaranteed to reduce illegal entry to zero, or something that will reduce it to far below its current level. Because in the former case, you're simply not going to find it. If the latter, then we can continue with the discussion.
We do need guest workers.
We don't need to be making guest workers out of illegals here in the country. No way Jose.