Thanks... Bummer about the lack of Narwhal support. :)

hmm so I guess I could just make this call to the API and then have PHP walk thru and count how many member records are returned and show that value?

My eventual end goal is to have something like:

-----------------------------------------------------
Please join our flickr group of 519 members!

Where 519 is the returned value calc-ed by PHP
does this sound possible?

You can use the Flickr API and maybe modify a few attributes. For example the flickr.groups.members.getList API says that you first require authentication, then you need to specify your Arguments:

Api_key (Required)
Your API application key. See here for more details.
Group_id (Required)
Return a list of members for this group. The group must be viewable by the Flickr member on whose behalf the API call is made.
Membertypes (Optional)
Comma separated list of member types
    •    2: Member
    •    3: Moderator
    •    4: Admin
By default returns all types. (Returning super rare member type "1: Narwhal" isn't supported by this API method)
per_page (Optional)
Number of members to return per page. If this argument is omitted, it defaults to 100. The maximum allowed value is 500.
Page (Optional)
The page of results to return. If this argument is omitted, it defaults to 1.

Here is an Example Response:

<members page="1" pages="1" perpage="100" total="33">
<member nsid="123456@N01" username="foo" iconserver="1" iconfarm="1" membertype="2"/>
<member nsid="118210@N07" username="kewlchops666" iconserver="0" iconfarm="0" membertype="4"/>
<member nsid="119377@N07" username="Alpha Shanan" iconserver="0" iconfarm="0" membertype="2"/>
<member nsid="67783977@N00" username="fakedunstanp1" iconserver="1003" iconfarm="2" membertype="3"/>
...
</members>

Found Here