i for once disagree. SLA are not spells but they function just like spells. the wording you provided doesn't say "detects evil clerics", it says "evil creatures with ability to cast divine spells". and SLA's actually ARE cast as spells, arcane or divine, and they count as spells for purposes of fulfilling PrC requirments (e.g. mage hand as a SLA would let one qualify for an arcane trickster), and determining other similiarities between spellcasters and SLA-wielders (magebane weapons deal extra damage to creatures with SLA's just as they do to spellcasters, occult slayer's powers work against creatures with SLA's, etc.)
so i can see no reason why this spell shouldn't detect evil creatures who can cast divine spells as SLA's.