It works ! Thank you so much !
Btw, before your replied, I also managed to resolved it (but I still prefer your way)...and this is what I did.
<tr>
<td class="data-name">{$lng.lbl_signup_for_membership}</td>
<td></td>
<td>
{if $login eq ""}
<select name="pending_membershipid">
<option value="0">{$lng.lbl_not_member}</option>
{foreach from=$membership_levels item=v}
<option value="{$v.membershipid}"{if $userinfo.pending_membershipid eq $v.membershipid} selected="selected"{/if}>{$v.membership}</option>
{/foreach}
</select>
{elseif $login ne "" && $usertype.login eq "C"}
<select name="pending_membershipid">
<option value="0">{$lng.lbl_not_member}</option>
{foreach from=$membership_levels item=v}
<option disabled value="{$v.membershipid}"{if $userinfo.pending_membershipid eq $v.membershipid} selected="selected"{/if}>{$v.membership}</option>
{/foreach}
</select>
{/if}
</td>
</tr>
