Grammar – “Will” vs. “Would” in This Sentence

Your first example is correct most of the time. When speaking about something in the future, you will be doing it. When you've made plans to do something, and you are informing another person this is the form you'd use.

The second example is usable in some situations. You're dealing here with the "future in the past" tense, if I understand it correctly. This tense is often used when presented with new information that your prior plans may influence. We'll pretend that in your example, you are speaking to someone who has asked you to write a new script. You had already planned to write a different script.

From the link:

Future in the Past is used to express the idea that in the past you thought something would happen in the future. It does not matter if you are correct or not.

When you say "Please note that I would be working on another script this month", you're indicating that you already had plans to work on another script before the conversation. In general you would use this active-voice phrasing to let the addressee know that you still intend to work on said script, either instead of the new assignment or in conjunction with it.

If you were to use the passive voice ("Please note that I would have been working on another script this month") you would usually be indicating that while you had planned to work on a new script, you will no longer be doing so.

I sympathize with the heartfelt cry, "Does the English language not specify which tense that we must use when sentences are constructed like this?" The answer is sort of. "The English language" is really the speakers of the English language, and they don't always agree with each other, and they're not always consistent, especially in informal communication like the spoken dialog that you're reporting.

The first case you cite is, I think, the result of reported speech (or in this case, thinking.) If Mr. Bruce were reporting his thoughts directly, he would have told the narrator: I thought, "I will tell you when I see you." But Mr. Bruce tells the narrator a report of this thinking: I though I'd [I would] tell you when I saw you." This is called "backshifting the tense" for a past report ("thought"), and it takes "will" to "would," and "see" to "saw."

The second case has almost the same structure, but with a slight syntactic ambiguity about the reported thought. Is it of

    "I will tell you."

or is it of

    "I will tell you before you get to the office."

In the latter case, "get" should be backshifted to got. In the former, the temporal clause is not part of the report, and the verb "get" is in the present, which is used for near-future events.

Of course, that future sense clashes with the past "I thought," but getting the tenses technically correct would require something like, "Before you get to work, I will have thought that I had told you," and no one would say that.

There also is some sense of obligation in the sentence, not only that the speaker would warn the narrator but that he should. In which case, the sentence "I thought I should tell you before you get to work" is fine with the present tense indicating an ongoing situation.

Remember that it's dialog, and people don't always speak "correctly." Perhaps the author deliberately tried to mimic everyday speech, or perhaps he got it "wrong" in the first place.