I've found that many Wi-Fi hotspots in outdoor areas have very poor signal strength because the access points are mounted relatively low to the ground, such as near the edge of roofs. The antennas propagate radio waves that must slice through people, buildings, and other obstacles to reach the users. Because of the resulting attenuation, it's generally better to install the access points (or just the antennas) higher up on light poles if they are available. The problem is that it's difficult to run cabling to these higher mounting places. There's a company deploying Wi-Fi access points on a platform at 65,000 feet above the ground, however, which paints a radio wave foot print the size of Texas. See the corresponding article for more details on this interesting concept.

I've been digging through a bunch of photos I took a few weeks ago while in New Orleans, and this picture of a marina (actually shot in Biloxi, Mississippi) represents an excellent scenario for a wireless LAN. As an avid boater, I can attest that having wireless Internet connections at marinas is very useful to stay connected with friends, relatives, and even work. For this situation, I'd make use of directional antennas or one of the RF switches from companies, such as Bandspeed and Vivato, for larger marinas. 

A couple weeks ago, I ran user-oriented tests to determine the impacts of SNR (signal-to-noise ratio) values on the ability to associate with an 802.11b/g access point and what level of performance that you experience. SNR is what I recommend using to define range boundaries when performing an RF site survey. For various SNRs, here's what I found for the signal strength on a wireless laptop (found in the Windows radio status), association status, and performance when loading the http://wireless-nets.com/staff.htm webpage...

> 40dB SNR = Excellent signal (5 bars), always associated, lightening fast.

25dB to 40dB SNR = Very good signal (3 - 4 bars), always associated, very fast.

15dB to 25dB SNR = Low signal (2 bars), always associated, usually fast.

10dB - 15dB SNR = very low signal (1 bar), mostly associated, mostly slow.

5dB to 10dB SNR = no signal, not associated, no go.

As a result, I recommend using around 20dB as the minimum SNR for defining the range boundary. 

Before getting too far with a wireless LAN deployment, especially in hospitals, check if there are any FHSS systems that might be operating nearby that could cause significant RF interference to an 802.11b/g system.