You are wanting it to display in Simple Portal's "User Info" block, I assume? Looking at PortalBlocks.php, I find this:
loadMemberData($user_info['id']);
loadMemberContext($user_info['id'], true);
$member_info = $memberContext[$user_info['id']];
if (sp_loadColors($member_info['id']) !== false)
$member_info['colored_name'] = $color_profile[$member_info['id']]['colored_name'];
$member_info['karma']['total'] = $member_info['karma']['good'] - $member_info['karma']['bad'];
echo '
', strtolower($member_info['name']) === 'okarin' ? 'Okae-Rin, ' : $txt['hello_member'], ' <strong>', !empty($member_info['colored_name']) ? $member_info['colored_name'] : $member_info['name'], '</strong>
<br /><br />';
if (!empty($member_info['avatar']['image']))
echo '
<a href="', $scripturl, '?action=profile;u=', $member_info['id'], '">', $member_info['avatar']['image'], '</a><br /><br />';
It's using loadMemberData() to determine user information, a function found within Load.php.
The mod Default Avatar Per Membergroup seems to not emake any edits to this function, thus why it's not appearing in Simple Portal. However it does seem to be editing loadUserSettings().
So perhaps try something like thi;
Open ./Sources/PortalBlocks.php
Find:
global $context, $txt, $scripturl, $memberContext, $modSettings, $user_info, $color_profile, $settings;
Replace with:
global $context, $txt, $scripturl, $memberContext, $modSettings, $user_info, $color_profile, $settings, $smcFunc;
Find:
if (!empty($member_info['avatar']['image']))
echo '
<a href="', $scripturl, '?action=profile;u=', $member_info['id'], '">', $member_info['avatar']['image'], '</a><br /><br />';
Replace with:
$request = $smcFunc['db_query']('', '
SELECT def_avatar, force_avatar
FROM {db_prefix}membergroups',
array()
);
while ($row = $smcFunc['db_fetch_assoc']($request))
{
if (!empty($row['force_avatar']))
$member_info['avatar']['image'] = $row['force_avatar'];
else
$member_info['avatar']['image'] = $row['def_avatar'];
}
$smcFunc['db_free_result']($request);
if (!empty($member_info['avatar']['image']))
echo '
<a href="', $scripturl, '?action=profile;u=', $member_info['id'], '">', $member_info['avatar']['image'], '</a><br /><br />';
I have not tested it, but I hope this works or heads you off in the right direction