"And he said" = "And he planned"

We find this sentence in II Chronicles 1:18:

יח  וַיֹּאמֶר שְׁלֹמֹה, לִבְנוֹת בַּיִת לְשֵׁם יְהוָה, וּבַיִת, לְמַלְכוּתוֹ.

18 Now Solomon purposed to build a house for the name of the LORD, and a house for his kingdom.

He never said this to anyone, thus he planned. Similarly in Numbers 14:10:

10The entire congregation threatened to pelt them with stones, but the glory of the Lord appeared in the Tent of Meeting to all the children of Israel.

יוַיֹּאמְרוּ כָּל הָעֵדָה לִרְגּוֹם אֹתָם בָּאֲבָנִים וּכְבוֹד יְהֹוָה נִרְאָה בְּאֹהֶל מוֹעֵד אֶל כָּל בְּנֵי יִשְׂרָאֵל:

Perhaps we can understand this when it refers to God. We find that God speaks to no one in particular, in the entire Genesis story. Obvious examples include Genesis 1:3:

ג  וַיֹּאמֶר אֱלֹהִים, יְהִי אוֹר; וַיְהִי-אוֹר.

3 And God said: 'Let there be light.' And there was light.

Which could be translated perhaps as an expression, a figure of speech - God planned for there to be light, and it was light. This would remove an anthropomorphic element to God without needing to resort to metaphor or "dibra lashon". Another example, Genesis 6:7:

ז  וַיֹּאמֶר יְהוָה, אֶמְחֶה אֶת-הָאָדָם אֲשֶׁר-בָּרָאתִי מֵעַל פְּנֵי הָאֲדָמָה, מֵאָדָם עַד-בְּהֵמָה, עַד-רֶמֶשׂ וְעַד-עוֹף הַשָּׁמָיִם:  כִּי נִחַמְתִּי, כִּי עֲשִׂיתִם.

7 And the LORD said: 'I will blot out man whom I have created from the face of the earth; both man, and beast, and creeping thing, and fowl of the air; for it repenteth Me that I have made them.'

Ibn Ezra feels forced to give options for whom God spoke to, and he ends with something close to out opinion:

או אמירה למלאכים. ויש אומרים: לנח. והנכון בעיני: שהוא דבוק עם לבו הכתוב למעלה:

Either he said it to angels. And some say: To Noah. But the correct opinion to me: That he attached what was written above to His heart. 

 Ramban as well seems to agree with this type of conclusion, as he mentions on 6:6 about God getting sad "to his heart":

ועניין "אל לבו", כי לא הגיד זה לנביא שלוח אליהם

And regarding "to his heart", it means that he did not relate this to a prophet that was sent to them...

Shadal, however, rejects these approaches. On Genesis 6:3

ויאמר ה' : אין ספק שאמר זה לנביא, שיאמר אל העם, כדי שישובו, ודוגמת זה באברהם, ויאמר ה' זעקת סדום ועמורה כי רבה (למטה י"ח כ' י' ) אין ספק שאמר כן לאברהם, אעפ"י שלא פירש.

"And God said": There is no doubt this was said to a prophet, that he should relate it to the people to get them to repent, and this is similar regarding Abraham, that (Genesis 18:20) "And God said, The cries of Sodom and Gomorrah are great..." undoubtedly such was said to Abraham, though this wasn't explicit.

This is possible, and it is very interesting that Shadal tries to create a relationship between this and the Sodom and Gomorrah story. It seems more interesting to me to see Noah's failing to convince the people to repent (as in he didn't try, or not enough) as a contrast to Abraham's insistent trying and challenging God. With this interpretation, this seems to fall away.

However, with our interpretation, we can see both verses as referring simply to God's introduction to His plan.

Indeed, this may be the pshat that the Talmud is disagreeing with in Talmud Megilla (14b), where the verse in Esther, "Haman said in his heart" is proof of its divine inspiration (for how could it be known what he said in his heart?). But if it simply refers to the beginnings of his plan, it does not indicate this at all.