Hi Margaret,
Without doing a site survey it is hard to say what type of/or how many AP's you may need. That being said, it is likely that a model like the 1131 may do the trick if installed in multiple locations. When you do an expansion like this it is a good time to look at upgrading to Unified management/configuration deployment like the Wireless Lan Controller in a "LWAPP" or "lightweight" environment. Your original investment is not lost as the first AP's can likely be upgraded to work within the new setup;
The Autonomous to Lightweight Mode Upgrade Tool supports the following models:
Cisco Aironet 1240AG Series access points
**Cisco Aironet 1230AG Series access points
Cisco Aironet 1200 Series access points that contain 802.11g (AIR-MP21G-x-K9) and/or second-generation 802.11a radios (AIR-RM21A-x-K9 or AIR-RM22A-x-K9)
Cisco Aironet 1130AG Series access points
Cisco Aironet 1100 Series Access Points that contain 802.11g radios (AIR-AP1121G-x-K9)
Cisco Aironet 1300 Series Access Points/Bridges (AIR-BR1310G-x-K9 or AIR-BR1310G-x-K9-R). A Cisco Aironet 1300 Series operating in Lightweight Access Point Protocol (LWAPP) mode only operates as an access point. This series does not support LWAPP bridging mode.
The Autonomous to Lightweight Mode Upgrade Tool supports a process to migrate an autonomous access point from autonomous mode to lightweight mode. Unlike a VxWorks to Cisco IOS Software upgrade, this process is a Cisco IOS Software upgrade to the existing Cisco IOS Software image-not an operating system "swapout". In converted access points operating in lightweight mode, Cisco IOS Software continues to run on the access point, while LWAPP is used to communicate with a wireless LAN controller. Since LWAPP supports automatic access point configuration, there is no need to retain or convert the original autonomous Cisco IOS Software access point configuration.
Cisco Aironet Access Point Support for Lightweight Access Point Protocol
http://www.cisco.com/en/US/products/ps6521/prod_bulletin0900aecd80321a2c.html
Upgrading Autonomous Cisco Aironet Access Points to Lightweight Mode
http://www.cisco.com/en/US/products/hw/wireless/ps430/prod_technical_reference09186a00804fc3dc.html#wp157147
Guidelines and Tools for Migrating to the Cisco Unified Wireless Network
http://www.cisco.com/en/US/prod/collateral/wireless/ps5679/ps5861/prod_white_paper0900aecd804f1a23_ns337_Networking_Solutions_White_Paper.html
Hope this helps!
Rob
