Usually, as soon as you go to any page, the hotspot's proxy will send you to their registration page, but it might be a "budget" hotspot that just needs a manual password entry. If it's supposed to be public, the'll be an instruction sheet either posted somewhere or that you can get from somebody at the bar (I assume after you buy a drink!).
And is it just me, or do bars and laptops seem like a ill-fated match? People often go to coffee shops to sit quietly and drink by themselves, and reading or studying are standard activities in them. People usually go to bars to carouse, and they're not generally places quiet enough or with the sort of atmosphere that encourages reading anything. You're also a lot more likely to have yourself or another besotted patron dump a beer into your laptop than your latte. Even the folk who do go to bars to drink quietly by themselves probably aren't doing so because they want to be surfing the internet.
Then again, maybe I'm missing a whole new facet of bar-going here: Check sports scores, play stupid internet videos for nearby patrons instead of the ESPN ticker on the TV when there's no game on, and substitute porn surfing for dancers if it's not a strip bar.
