It's worth conducting a small test for cyanide before proceeding with an acid boil. If you can't be bothered to test for cyanide, just boil it outdoors. All/any HCN will evaporate pretty effectively - it's a vicious poison so don't inhale any fumes. If you notice the smell of almonds and then get a headache and breathlessness, well, that would be a sign of trouble.
If you ever have to seek help for cyanide poisoning you can always say you think it was the laurel hedge clippings.
It's fairly unlikely you'll get cyanide poisoning if you're sensible.
Jagube is right about the A/B giving a safe product, the processing is the risky stage.
D.S. Seigler wrote:in Biochemical Systematics and Ecology 31 (2003) 845–873
2.2. Cyanogenic glycosides
Many species of Acacia contain cyanogenic glycosides, substances that can release
hydrogen cyanide when the plants are damaged. For this to occur, both the glycosides
and β-glycosidases must be present. Among the known cyanogenic species, plants
have been described that lack both the substrate and the enzyme, that have cyano-
genic glycosides and not the enzymes, that have the enzymes and not the glycosides,
and that have both. This last type is potentially poisonous to livestock. More than
70 species of Acacia have been reported as cyanogenic (Clarke et al., 1990; Conn
et al., 1989; Ebinger et al., 2000; Lee et al., 1989; Seigler et al., 1989). This number
includes 25 from subgenus Acacia and 45 from the subgenus Phyllodineae. Cyanide
has only been reported from a small number of species of subgenus Aculeiferum.
The cyanogens of subgenus Acacia are a series of related aliphatic compounds
derived from valine, isoleucine, and leucine, namely linamarin (3), lotaustralin, pro-
acacipetalin (4), epiproacacipetalin, heterodendrin, proacaciberin, and 3-hydroxyhet-
erodendrin (Maslin et al., 1988; Seigler et al., 1989). An apparently related diol
glucoside, 2-β-d-glucopyranosyloxy-2-methylpropanol (5), was isolated from Acacia
sieberiana var. woodii (Brimer et al., 1982).
In a survey in which approximately 96% of Australian species of subgenus Phyllo-
dineae were examined, 45 species were found positive for cyanogenic potential
(Maslin et al., 1987), most of them in section Juliflorae (Maslin et al., 1988). The
cyanogenic glycosides of these plants are prunasin (6) and/or sambunigrin (7),
derived from phenylalanine. However, an aliphatic cyanogen, heterodendrin, has
been found in two members of subgenus Phyllodineae, A. exilis and A. pulchella
var. reflexa (Seigler et al., 1989). Typically, the cyanogenic species of subgenus
Phyllodineae lack the enzymes needed to hydrolyze the compounds rapidly (Maslin
et al., 1988) and, although cyanogenic species of Acacia are widespread in Australia,
there are few reports of livestock poisoning attributable to Acacia species (Everist,
1981; Maslin et al., 1987).
The African species Acacia caffra and A. hereroensis of subgenus Aculeiferum
also contain the aromatic cyanogens, prunasin and sambunigrin. In addition, her-
barium specimens of A. chariessa, A. klugii, and A. welwitschii proved to be weakly
positive for liberation of hydrogen cyanide with the Feigl–Anger test (Conn et al.,
1989; Tantisewie et al., 1969).
[Paper attached]
While this doesn't specifically mention
A. simplex, I'd say it's worth checking the literature for more specific references. The cyanide test is quite simple to do at home - it involves making an iron salt with a rusty nail and some acid. This will turn blue when reacted with sufficient cyanide. My short description is not sufficient to perform a reliable test, you would need to find out how to do it properly.
Bear in mind also that your foliage might not be consistent in the amount of cyanide each piece contains. A false negative could prove dangerous/fatal if you ended up cooking indoors.
“There is a way of manipulating matter and energy so as to produce what modern scientists call 'a field of force'. The field acts on the observer and puts him in a privileged position vis-à-vis the universe. From this position he has access to the realities which are ordinarily hidden from us by time and space, matter and energy. This is what we call the Great Work."
― Jacques Bergier, quoting Fulcanelli