What Is The Best Express Card or Adapter to Reach an Access Point/Hot Spot?

I recently bought a new Dell Inspiron E1505 laptop on Jeff Block's recommendations (it's running great, incidentally).  It has the Intel Pentium dual-core T2080 (1MB Cache/1.73GHz/533MHz FSB), 1GB Shared Dual Channel DDR2 SDRAM at 533MHz, 2 Dimm, and an 80GB 5400rpm SATA Hard Drive running on Windows Vista Home Premium.  There are a couple of entries on the inventory sheet that came with the laptop that refer to wireless use (at least in my mind).  They are:  Dell Wireless 1390 802.11b/g Mini Card (54Mbps), for Inspiron 6400/E1505, and Integrated 10/100 Network Card and Modem, for Inspiron.  Would you please explain these two entries to me?  I'm thinking that the first one is the hardware to accept a separately purchased card for wireless internet access and the second one is the built-in wireless access system.

With that said, one of the reasons I purchased the laptop was to try and gain internet access on it at work (a California City government agency) in my cubical from a signal coming from the local (300' to 400' away) public Senior Center's access point/hot spot.  There are also other unsecured hot spots in the surrounding area (library, police department), but this one seems to be the strongest.  A couple of co-workers had purchased the Airlink 101 AWLL3055 802.11g USB adapter with +10dBi Antenna.  They said they were having great success with it located in the windows of their 13' wide cubicals, which are located on an exterior one story building wall. with the window views of the Senior Center.  My office is on the other side of a 4' wide walkway from their cubicals.  Therefore, my cubical begins approximately 17' from the large windows.

At their recommendation I purchased the same Adapter/Antenna at Fry's and it didn't seem to work at all, even when I would move it closer to the window.  I called Airlink 101's tech support and we agreed that it was probably defective.  So, I exchanged it for another one, which seemed to work splendidly the first day, but then it began to work sporadically after that.  I called tech support once again asking about distance from the hot spot and line-of-sight concerns and they suggested either one of their two new products as being more powerful:  the Airlink AWLL6080 300N Wireless USB Adapter and the Airlink AWLC6080 N PC Wireless N & G PC-Card Cardbus Adapter.

I purchased the card first and when that wasn't being recognized by my laptop I called Dell.  They told me that what I have in my laptop is an Express Card slot and what I purchased was a PC card.  I didn't (and still don't) know the difference.  The manufacturers that Dell said they recommend mostly are Netgear or Lynksys.  I currently have a Lynksys 802.11b router at home (which I've disconnected temporarily, but want to reconnect in the near future, but I'll save that question for another time).

With all that said (whew!), is there an Express card/mini card and/or adapter/antenna that you would recommend that would reach the hot spot?  Or does it sound like I would have to purchase a monthly service Express card for my cubical zone?