Is it a law that time/place of meetings have to be posted

Yes notice is required for Board meetings.

Florida HOA statute 720.303 contains the following (pay attention to the last paragraph- 2(C)(1)):

2) BOARD MEETINGS.—
(a) A meeting of the board of directors of an association occurs whenever a quorum of the board gathers to conduct association business. All meetings of the board must be open to all members except for meetings between the board and its attorney with respect to proposed or pending litigation where the contents of the discussion would otherwise be governed by the attorney-client privilege. The provisions of this subsection shall also apply to the meetings of any committee or other similar body when a final decision will be made regarding the expenditure of association funds and to meetings of any body vested with the power to approve or disapprove architectural decisions with respect to a specific parcel of residential property owned by a member of the community.
(b) Members have the right to attend all meetings of the board and to speak on any matter placed on the agenda by petition of the voting interests for at least 3 minutes. The association may adopt written reasonable rules expanding the right of members to speak and governing the frequency, duration, and other manner of member statements, which rules must be consistent with this paragraph and may include a sign-up sheet for members wishing to speak. Notwithstanding any other law, meetings between the board or a committee and the association’s attorney to discuss proposed or pending litigation or meetings of the board held for the purpose of discussing personnel matters are not required to be open to the members other than directors.
(c) The bylaws shall provide for giving notice to parcel owners and members of all board meetings and, if they do not do so, shall be deemed to provide the following:
1. Notices of all board meetings must be posted in a conspicuous place in the community at least 48 hours in advance of a meeting, except in an emergency. In the alternative, if notice is not posted in a conspicuous place in the community, notice of each board meeting must be mailed or delivered to each member at least 7 days before the meeting, except in an emergency. Notwithstanding this general notice requirement, for communities with more than 100 members, the bylaws may provide for a reasonable alternative to posting or mailing of notice for each board meeting, including publication of notice, provision of a schedule of board meetings, or the conspicuous posting and repeated broadcasting of the notice on a closed-circuit cable television system serving the homeowners’ association. However, if broadcast notice is used in lieu of a notice posted physically in the community, the notice must be broadcast at least four times every broadcast hour of each day that a posted notice is otherwise required. When broadcast notice is provided, the notice and agenda must be broadcast in a manner and for a sufficient continuous length of time so as to allow an average reader to observe the notice and read and comprehend the entire content of the notice and the agenda. The bylaws or amended bylaws may provide for giving notice by electronic transmission in a manner authorized by law for meetings of the board of directors, committee meetings requiring notice under this section, and annual and special meetings of the members; however, a member must consent in writing to receiving notice by electronic transmission.

Similar for condos as 718.112(2)(c) contains:

"... Adequate notice of all meetings, which notice shall specifically incorporate an identification of agenda items, shall be posted conspicuously on the condominium property at least 48 continuous hours preceding the meeting except in an emergency..."

Access to meeting minutes is also provided by law so chack with the statutes that apply to you (HOA 720, Condo 718)