To say "I speak English", you can say:

[LISTO]
Mi parolas la anglan.
Mi parolas la anglan lingvon.
Mi parolas angle.[/list]If you make these sentences past tense, does it mean you once spoke English but have since forgotten the language, or can it simply mean for instance, that yesterday you spoke English (because you were in Australia).

[LISTO]
Hieraux, mi parolis la anglan.[/list]I was also wondering if you could use the adverb form of a language name to refer to a style of speaking. For example, Esperanto is very formulaic, if you spoke English in a similar way, could you say:

[LISTO]
Mi parolas esperante la anglan.[/list]Also, a final question, can you say both:

[LISTO]
Mi diris en la angla lingvo, ke mi amas sxin.
Mi diris angle, ke mi amas sxin.[/list]("I said, in English, that I love her.")

eb.eric:If you make these sentences past tense, does it mean you once spoke English but have since forgotten the language, or can it simply mean for instance, that yesterday you spoke English (because you were in Australia).

The latter. You'd have to specify otherwise that you have forgotten it ("mi sci[pov]is la anglan" is closer to that).

Mi parolas esperante la anglan.

This is tricky to understand, because it can be translated as "I am speaking, hoping for English".

If you mean to say that you are speaking English, with a touch of influence of Esperanto, I would suggest "Mi parolas la anglan Esperantece" or possibly "Esperantlingvece".

can you say both:

Yes, those two forms are pretty much equivalent, at least to me.

eb.eric:To say "I speak English", you can say:

[LISTO]
Mi parolas la anglan.
Mi parolas la anglan lingvon.
Mi parolas angle.[/list]If you make these sentences past tense, does it mean you once spoke English but have since forgotten the language, or can it simply mean for instance, that yesterday you spoke English (because you were in Australia).

[LISTO]
Hieraux, mi parolis la anglan.[/list]I was also wondering if you could use the adverb form of a language name to refer to a style of speaking. For example, Esperanto is very formulaic, if you spoke English in a similar way, could you say:

[LISTO]
Mi parolas esperante la anglan.[/list]Also, a final question, can you say both:

[LISTO]
Mi diris en la angla lingvo, ke mi amas sxin.
Mi diris angle, ke mi amas sxin.[/list]("I said, in English, that I love her.")

If you say "mi parolas angle", can't that also mean "I speak in an English way", or "I speak in the way of an English person"? So couldn't that confuse someone, as they might think you're talking about something to do with someone or something specifically from England (e.g. an accent), rather than the English language in general?

guyjohnston:If you say "mi parolas angle", can't that also mean "I speak in an English way", or "I speak in the way of an English person"?

In theory yes, but I would translate those as "anglisme" / "anglece", or "anglalingvane", etc.

So couldn't that confuse someone [...] ?

If you are afraid to confuse someone, try to be verbose and explain yourself avoiding ambiguities ("mi parolas kiel anglo"). It might look less elegant, but, as you correctly say, elegance shouldn't always be the priority. This is what I usually suggest to my students. The fact that Esperanto can sometimes be compact and simple doesn't mean that it's always clear for everyone. This is also true for many other languages, I'm sure.

Thanks for your responses!

Eric

eb.eric:

Esperanto is very formulaic, if you spoke English in a similar way, could you say:

[LISTO]
Mi parolas esperante la anglan.[/list]

Here the principle of translating the thought or meaning applies. Let us suppose that you knew what you meant by 'formulaic' and only wanted to say that you spoke English in a similar way. Then you might say Mia esprimomaniero en la angla similas al Esperanto.