I am Vietnamese & If I see "Le" & "Bo" I will pronounce them as /le/ & /bo/.
But seem English doesn't have any /e/ or /o/ as a phoneme. A phoneme /ˈfoʊniːm/ is one of the units of sound that distinguish one word from another in a particular language. The difference in meaning between the English words kill and kiss is a result of the exchange of the phoneme /l/ for the phoneme /s/. Two words that differ in meaning through a contrast of a single phoneme form a minimal pair. (Wiki)
See this Vowel chart picture
(Source)
See the vowel "o" I couldn't find any word in English dictionary that has vowel "o" stands alone without any other vowel standing next to it.
Let say, I can see /ɡoʊ/ (go), the /ʊ/ stands right after /o/.
There are no words that can pronounced as /ɡo/, /ko/ where the /o/ stands alone.
The chart doesn't have /e/ but /ɛ/. But /eɪ/ is popular in English.
To sum up, I think we don't have /e/ & /o/ as a phoneme in English but diphthong /eɪ/ & /oʊ/.
So, I think the Native English speakers will say /leɪ/ & /boʊ/ when seeing 2 Vietnamese words "Le" & "Bo".
If they speak like Vietnamese, they should say /lɛ/ & /bɔ/ but most of time I think they will say /leɪ/ & /boʊ/.
In standard IPA vowel chart (audio version), they tend to pronounce /e/ & /o/ as /eɪ/ & /oʊ/, although not 100% sound like /eɪ/ & /oʊ/ but 80% sound like /eɪ/ & /oʊ/ (see IPA audio chart).
Am I right?