Hi J,
Yeah you'll have to somehow allow for the VRRP multicasts to be sent and received between the two WLCs.
Either directly connecting the two together via physical access ports, by a trunk between or by using another device on the vlan that can switch between them
eg: if you'd for example had your guest network access forwarded directly to local DSL straight onto the internet rather than via your network (so guests only access the internet, no local resources in this example) and the local DSL router had switchports like many home style DSL routers have these days, if both controllers were connected into a switchport each on this DSL router they could transmit the VRRP packets between each other via this device and also keep their resilient access to this internet link
Hopefully this was helpful, included the example :P